AQA GCSE Combined Science: grade by grade

Every skill, from the first marks to the top grade. For each grade you also need the skills for the grades below it. Tick them off in the app's Notes section.

Grade 3

Grade 3 checklist (PDF)

Name eukaryotic and prokaryotic cells Animal and plant cells are eukaryotic; bacterial cells are prokaryotic. Eukaryotes and prokaryotes
Name the parts of an animal cell Nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Animal and plant cells
Name the extra structures in plant cells Chloroplasts, a permanent vacuole filled with cell sap, and a cell wall made of cellulose. Animal and plant cells
Name specialised animal and plant cells Sperm, nerve and muscle cells in animals; root hair, xylem and phloem cells in plants. Cell specialisation
State what cell differentiation is Differentiation is the process by which a cell becomes specialised for a particular function. Cell differentiation
State what magnification means How many times bigger the image is than the real object. Microscopy
State where chromosomes are found In the nucleus of a cell. Chromosomes
State what mitosis produces Two genetically identical cells. Mitosis and the cell cycle
State what a stem cell is An undifferentiated cell that can make more cells of the same type and can differentiate into other types of cell. Stem cells
Define diffusion The net movement of particles from an area of higher concentration to an area of lower concentration. Diffusion
Define osmosis The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane. Osmosis
State what active transport is The movement of substances from a more dilute solution to a more concentrated solution, against a concentration gradient. Active transport
Put the levels of organisation in order From smallest to largest: cell → tissue → organ → organ system → organism. Principles of organisation
Name the organs of the digestive system Mouth and salivary glands, oesophagus, stomach, liver, gall bladder, pancreas, small intestine and large intestine. The human digestive system
Name the three types of blood vessel Arteries carry blood away from the heart, veins carry blood back to the heart, and capillaries link them inside tissues. The heart and blood vessels
Name the four components of blood Plasma, red blood cells, white blood cells and platelets. Blood
Name the vessels that supply heart muscle The coronary arteries supply the heart muscle with oxygenated blood. Coronary heart disease: a non-communicable disease
Define health Health is the state of physical and mental well-being. Health issues
Define a risk factor A factor linked to an increased rate of a disease, such as part of a person's lifestyle or a substance in their body or environment. The effect of lifestyle on some non-communicable diseases
Define cancer Cancer is the result of changes in cells that lead to uncontrolled growth and division. Cancer
Name the tissues in a leaf Upper and lower epidermis, palisade mesophyll, spongy mesophyll, xylem and phloem, with guard cells around the stomata. Plant tissues
Name the parts of the plant transport system The roots, stem and leaves form an organ system; xylem carries water and phloem carries sugars. Plant organ system
Define a pathogen A pathogen is a microorganism that causes infectious (communicable) disease. Communicable (infectious) diseases
Name the four types of pathogen Viruses, bacteria, fungi and protists; they can infect both animals and plants. Communicable (infectious) diseases
Name viral diseases of humans and plants Measles and HIV in humans; tobacco mosaic virus (TMV) in plants. Viral diseases
Name two bacterial diseases Salmonella food poisoning and gonorrhoea, a sexually transmitted disease. Bacterial diseases
Name a fungal disease of plants Rose black spot is a fungal disease of roses. Fungal diseases
Name a disease caused by a protist Malaria is caused by a single-celled protist. Protist diseases
Name the body's non-specific defences The skin, the nose, the trachea and bronchi, and the stomach. Human defence systems
State what a vaccine contains Small quantities of a dead or inactive form of a pathogen. Vaccination
State what antibiotics do Antibiotics, such as penicillin, kill infective bacteria inside the body, curing bacterial diseases. Antibiotics and painkillers
State what painkillers do Painkillers treat the symptoms of a disease but do not kill pathogens. Antibiotics and painkillers
Match drugs to their original sources Digitalis from foxgloves, aspirin from willow, and penicillin from Penicillium mould (discovered by Alexander Fleming). Discovery and development of drugs
Write the word equation for photosynthesis carbon dioxide + water → glucose + oxygen, with light written above the arrow. Photosynthetic reaction
State where photosynthesis takes place In the chloroplasts of plant and algal cells, where chlorophyll absorbs light. Photosynthetic reaction
Name the factors affecting photosynthesis rate Temperature, light intensity, carbon dioxide concentration and the amount of chlorophyll. Rate of photosynthesis
List the five uses of glucose Respiration, starch for storage, fats or oils for storage, cellulose for cell walls, and amino acids for proteins. Uses of glucose from photosynthesis
State why organisms need energy For chemical reactions that build larger molecules, for movement and for keeping warm. Aerobic and anaerobic respiration
Write the word equation for aerobic respiration glucose + oxygen → carbon dioxide + water. Aerobic and anaerobic respiration
State how exercise changes heart and breathing Heart rate, breathing rate and breath volume all increase. Response to exercise
Define metabolism Metabolism is the sum of all the reactions in a cell or the body. Metabolism
Define homeostasis Regulating the internal conditions of a cell or organism to keep them at the optimum, in response to internal and external changes. Homeostasis
Name conditions controlled by homeostasis In humans: blood glucose concentration, body temperature and water levels. Homeostasis
State what the nervous system does It lets you react to your surroundings and coordinates your behaviour. The human nervous system
Define a hormone A chemical secreted by a gland directly into the bloodstream, which carries it to a target organ. Human endocrine system
Name the organ that controls blood glucose The pancreas monitors and controls blood glucose concentration. Control of blood glucose concentration
Name the main male and female hormones Testosterone from the testes; oestrogen from the ovaries. Hormones in human reproduction
Name hormonal and non-hormonal contraceptive methods E.g. the pill, implant, condom, diaphragm, IUD, spermicide, abstinence and sterilisation. Contraception
Name the gametes in animals and plants Animals: sperm and egg cells. Flowering plants: pollen and egg cells. Sexual and asexual reproduction
State how many parents each type needs Sexual reproduction needs two parents; asexual reproduction needs only one. Sexual and asexual reproduction
State where and why meiosis happens Cells in the reproductive organs divide by meiosis to form gametes. Meiosis
State where DNA is found The genetic material in the nucleus is a chemical called DNA, contained in chromosomes. DNA and the genome
Define dominant and recessive alleles A dominant allele is expressed even with one copy; a recessive allele is expressed only with two copies. Genetic inheritance
Describe polydactyly and cystic fibrosis Polydactyly is having extra fingers or toes; cystic fibrosis is a disorder of cell membranes. Inherited disorders
State the number of chromosome pairs Ordinary human body cells contain 23 pairs of chromosomes. Sex determination
Define variation Differences in the characteristics of individuals in a population. Variation
Define evolution A change in the inherited characteristics of a population over time through natural selection. Evolution
Define selective breeding Humans breeding plants and animals for particular genetic characteristics. Selective breeding
State that evolution is widely accepted The theory of evolution by natural selection is now widely accepted. Evidence for evolution
Define a fossil The remains of organisms from millions of years ago, which are found in rocks. Fossils
Define extinction A species is extinct when there are no remaining individuals of that species still alive. Extinction
Name an antibiotic-resistant bacterium MRSA is resistant to antibiotics. Resistant bacteria
List the Linnaean groups in order Kingdom, phylum, class, order, family, genus, species. Classification of living organisms
Define population, community, habitat and ecosystem A population is one species in a habitat, a community is all the populations there, and an ecosystem is the community interacting with the non-living environment. Communities
Define an abiotic factor A non-living factor in the environment that can affect a community. Abiotic factors
Define a biotic factor A living factor, such as another organism, that can affect a community. Biotic factors
Define an adaptation A feature that helps an organism survive in the conditions where it normally lives. Adaptations
Name producers and consumers in a food chain The producer comes first, then the primary, secondary and tertiary consumers. Levels of organisation
State that materials are recycled in ecosystems Materials cycle through the living and non-living parts of an ecosystem, providing the building blocks for new organisms. How materials are cycled
Define biodiversity The variety of all the different species of organisms on Earth, or within an ecosystem. Biodiversity
Name sources of water, air and land pollution Water: sewage, fertiliser, toxic chemicals. Air: smoke, acidic gases. Land: landfill, toxic chemicals. Waste management
Name ways humans use land Building, quarrying, farming and dumping waste. Land use
Define deforestation Cutting down large areas of forest so the land can be used for something else. Deforestation
Name two gases that contribute to global warming Carbon dioxide and methane. Global warming
Name programmes that protect biodiversity Breeding programmes, protecting rare habitats, hedgerows and field margins, reducing deforestation and carbon dioxide emissions, and recycling. Maintaining biodiversity
Tell elements from compounds using formulae An element's formula has one symbol (Fe, O₂); a compound's formula has two or more different symbols (CO₂, NaCl). Atoms, elements and compounds
Recall symbols of the first 20 elements Also the Group 1 and Group 7 elements and others in the course, with the correct capital and lower-case letters. Atoms, elements and compounds
Define a mixture Two or more elements or compounds that are not chemically combined together. Mixtures
State that models change with new evidence A scientific model may be changed or replaced when new experimental evidence doesn't fit it. The development of the model of the atom
Recall the charges of subatomic particles Proton +1, neutron 0, electron −1. Relative electrical charges of subatomic particles
State where each particle is found Protons and neutrons are in the nucleus; electrons are in shells around it. Relative electrical charges of subatomic particles
Recall relative masses of subatomic particles Proton 1, neutron 1, electron very small. Size and mass of atoms
Recall how many electrons each shell holds For the first 20 elements: 2 in the first shell, then up to 8 in the second and 8 in the third. Electronic structure
Identify groups and periods Groups are the vertical columns; periods are the horizontal rows. The periodic table
State how early tables were ordered By atomic weight, because protons, neutrons and electrons had not been discovered. Development of the periodic table
Locate metals and non-metals in the table Metals are on the left and towards the bottom; non-metals are on the right and towards the top. Metals and non-metals
Name Group 0 and some of its elements The noble gases: helium, neon, argon, krypton, xenon and radon. Group 0
Explain the name 'alkali metals' They react with water to form hydroxides that dissolve to give alkaline solutions. Group 1
Recall the halogens and their states At room temperature chlorine is a green gas, bromine a red-brown liquid and iodine a grey-black solid. Group 7
Name the three types of strong bond Ionic, covalent and metallic. Chemical bonds
State that metals lose and non-metals gain electrons Metal atoms lose outer electrons to form positive ions; non-metal atoms gain electrons to form negative ions. Ionic bonding
Describe an ionic compound as a giant structure It is a giant structure (lattice) of ions arranged in a regular pattern. Ionic compounds
Describe a covalent bond as a shared pair A covalent bond is a pair of electrons shared between two atoms. Covalent bonds are strong. Covalent bonding
State that metals have giant structures The atoms in a metal are arranged in a regular pattern in a giant structure. Metallic bonding
Name the changes of state Melting and freezing happen at the melting point; boiling and condensing happen at the boiling point. The three states of matter
Recall the four state symbols (s) solid, (l) liquid, (g) gas, (aq) aqueous: dissolved in water. State symbols
State that ionic compounds have high melting points Ionic compounds such as sodium chloride are solids at room temperature with high melting and boiling points. Properties of ionic compounds
State that small molecules have low boiling points Substances made of small molecules are usually gases or liquids at room temperature. Properties of small molecules
State that polymers have very large molecules Polymer molecules are long chains made of many repeating units. Polymers
Name examples of giant covalent structures Diamond and graphite (both forms of carbon) and silicon dioxide (silica). Giant covalent structures
State that pure metals can be bent and shaped The atoms in a pure metal are arranged in layers. Properties of metals and alloys
State that metals conduct electricity and heat Metals are good conductors of electricity and of thermal energy. Metals as conductors
State that diamond is a form of carbon Diamond is made only of carbon atoms, in a giant covalent structure. Diamond
Describe graphite as layers of carbon atoms Graphite is made of layers of carbon atoms arranged in hexagonal rings. Graphite
Describe graphene as one layer of graphite Graphene is a single layer of carbon atoms in hexagonal rings, one atom thick. Graphene and fullerenes
State the law of conservation of mass No atoms are lost or made in a reaction, so the mass of the products equals the mass of the reactants. Conservation of mass and balanced chemical equations
Count the atoms in a formula Multiply the small numbers by the big number in front, e.g. 2H₂O contains 4 hydrogen atoms and 2 oxygen atoms. Conservation of mass and balanced chemical equations
Read relative atomic masses from the periodic table A_r is the larger of the two numbers in each box, e.g. O = 16, Na = 23. Relative formula mass
State that gases can enter or leave In an open container, gases can escape into the air or react from the air. Mass changes when a reactant or product is a gas
Calculate a mean from repeat readings Add up the results, leaving out any anomalous ones, and divide by how many you added. Chemical measurements
Recall the unit of concentration Mass of solute per volume of solution, usually grams per dm³ (g/dm³). Concentration of solutions
Name the oxide formed by a metal A metal reacting with oxygen forms the metal oxide, e.g. magnesium + oxygen → magnesium oxide. Metal oxides
Recall the order of the reactivity series Potassium, sodium, lithium, calcium, magnesium, (carbon), zinc, iron, (hydrogen), copper, from most to least reactive. The reactivity series
Explain why gold is found as the metal Gold is so unreactive that it is found in the Earth as the metal itself, not as a compound. Extraction of metals and reduction
Name the products of metal + acid A salt and hydrogen, e.g. magnesium + hydrochloric acid → magnesium chloride + hydrogen. Reactions of acids with metals
Name the salt type from each acid Hydrochloric acid gives chlorides, nitric acid gives nitrates and sulfuric acid gives sulfates. Neutralisation of acids and salt production
Name reactants needed to make a salt For example, copper(II) oxide and sulfuric acid make copper(II) sulfate. Soluble salts
Use pH to classify solutions Below 7 is acidic, 7 is neutral and above 7 is alkaline. The pH scale and neutralisation
Name the electrodes and their charges The cathode is the negative electrode and the anode is the positive electrode. The process of electrolysis
State the products from molten lead bromide Lead is produced at the cathode and bromine at the anode. Electrolysis of molten ionic compounds
Define exothermic and endothermic reactions Exothermic reactions transfer energy to the surroundings so their temperature rises; endothermic reactions take in energy so their temperature falls. Energy transfer during exothermic and endothermic reactions
Give examples of exothermic reactions Combustion, many oxidation reactions and neutralisation are all exothermic. Energy transfer during exothermic and endothermic reactions
State what activation energy is The minimum amount of energy that particles must have to react when they collide. Reaction profiles
Say what the rate of reaction measures Rate is how quickly a reactant is used up or a product is formed. Calculating rates of reactions
Name the five factors that affect rate Concentration of solutions, pressure of gases, surface area of solids, temperature and the presence of a catalyst. Factors which affect the rates of chemical reactions
State that particles must collide to react A reaction can only happen when reactant particles collide with each other. Collision theory and activation energy
State what a catalyst does It increases the rate of a reaction but is not used up. Catalysts
Recognise the reversible reaction symbol ⇌ The ⇌ symbol shows that a reaction can go in both directions. Reversible reactions
Recall what exothermic and endothermic mean Exothermic reactions transfer energy to the surroundings; endothermic reactions take in energy from the surroundings. Energy changes and reversible reactions
State what crude oil is A finite resource found in rocks: the remains of an ancient biomass, mainly plankton, that was buried in mud. Crude oil, hydrocarbons and alkanes
Define a hydrocarbon A compound whose molecules are made of hydrogen and carbon atoms only. Crude oil, hydrocarbons and alkanes
Name fuels produced from crude oil Petrol, diesel oil, kerosene, heavy fuel oil and liquefied petroleum gases (LPG). Fractional distillation and petrochemicals
Name materials made by the petrochemical industry Solvents, lubricants, polymers and detergents. Fractional distillation and petrochemicals
Name the products of complete combustion A hydrocarbon burns completely in oxygen to form carbon dioxide and water. Properties of hydrocarbons
Define cracking Breaking down large hydrocarbon molecules into smaller, more useful molecules. Cracking and alkenes
Define a pure substance in chemistry A single element or a single compound, not mixed with any other substance. Pure substances
Define a formulation A mixture that has been designed as a useful product. Formulations
Give examples of formulations Fuels, cleaning agents, paints, medicines, alloys, fertilisers and foods. Formulations
Tell mixtures from pure substances on chromatograms A mixture gives two or more spots; a pure substance gives a single spot. Chromatography
Describe the test for hydrogen Hold a burning splint at the open end of a test tube of the gas. Test for hydrogen
State the positive result for hydrogen Hydrogen burns rapidly with a pop sound (a 'squeaky pop'). Test for hydrogen
Describe the test for oxygen Put a glowing splint into a test tube of the gas. Test for oxygen
State the positive result for oxygen The glowing splint relights (bursts back into flame). Test for oxygen
Describe the test for carbon dioxide Bubble the gas through limewater, or shake the gas with limewater. Test for carbon dioxide
State the positive result for carbon dioxide The limewater turns milky (cloudy). Test for carbon dioxide
Describe the test for chlorine Put damp litmus paper into the gas. Test for chlorine
State the positive result for chlorine The litmus paper is bleached and turns white. Test for chlorine
Name the two main gases in air Nitrogen makes up about four-fifths of the air and oxygen about one-fifth. The proportions of different gases in the atmosphere
Give the percentages of nitrogen and oxygen Air is about 80% nitrogen and about 20% oxygen. The proportions of different gases in the atmosphere
Say where the early atmosphere came from Intense volcanic activity during the Earth's first billion years released the gases that formed it. The Earth's early atmosphere
Name the process that produced the oxygen Photosynthesis by algae and plants produced the oxygen that is now in the atmosphere. How oxygen increased
Name a process that removed carbon dioxide Photosynthesis by algae and plants took carbon dioxide out of the atmosphere. How carbon dioxide decreased
Name three greenhouse gases Water vapour, carbon dioxide and methane are greenhouse gases. Greenhouse gases
Give two activities that release carbon dioxide Burning fossil fuels and deforestation both increase the carbon dioxide in the atmosphere. Human activities which contribute to an increase in greenhouse gases in the atmosphere
State a major cause of climate change An increase in the average global temperature is a major cause of climate change. Global climate change
Give one way to reduce carbon dioxide emissions For example, generate electricity from renewable resources instead of burning fossil fuels. The carbon footprint and its reduction
Name the products of complete combustion A fuel containing carbon and hydrogen forms carbon dioxide and water when it burns in plenty of oxygen. Atmospheric pollutants from fuels
State that carbon monoxide is toxic Carbon monoxide is a toxic (poisonous) gas. Properties and effects of atmospheric pollutants
State what humans use Earth's resources for To provide warmth, shelter, food and transport. Using the Earth's resources and sustainable development
State what potable water means Potable water is water that is safe to drink. Potable water
Say why waste water must be treated Towns and industry produce large amounts of waste water that must be treated before it is released into the environment. Waste water treatment
Name the four stages of an LCA Extracting and processing raw materials, manufacturing and packaging, use and operation, and disposal. Life cycle assessment
State the three ways to reduce resource use Reduce use, reuse and recycle. Ways of reducing the use of resources
Define a system A system is an object or a group of objects that you choose to study, e.g. a ball and the Earth. Energy stores and systems
Name the main energy stores Kinetic, gravitational potential, elastic potential, thermal (internal), chemical, magnetic, electrostatic and nuclear. Energy stores and systems
Recall the kinetic and gravitational energy equations E_k = ½ m v² and E_p = m g h: the specification says you must be able to recall both. Changes in energy
Name what affects the energy needed to heat The energy needed depends on the mass, the material and the temperature rise. Energy changes in systems
State the unit of power Power is measured in watts (W); 1 W is 1 joule transferred per second. Power
State the law of conservation of energy Energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed. Energy transfers in a system
Identify useful and wasted energy transfers E.g. for a lamp, light is the useful output and heating the surroundings is wasted. Efficiency
List the main energy resources Fossil fuels (coal, oil, gas), nuclear fuel, bio-fuel, wind, hydro-electricity, geothermal, the tides, the Sun and water waves. National and global energy resources
Define a renewable energy resource A resource that is being (or can be) replenished as it is used. National and global energy resources
Name common components from their symbols Recognise the cell, battery, switch, lamp, resistor, ammeter and voltmeter symbols. Standard circuit diagram symbols
State that current is a flow of charge Electric current is a flow of electrical charge around a closed circuit. Electrical charge and current
Give the units of charge, current, time Charge in coulombs (C), current in amperes (A) and time in seconds (s). Electrical charge and current
State the unit of resistance Resistance is measured in ohms (Ω). Current, resistance and potential difference
Recall that an LDR's resistance falls in light The resistance of an LDR decreases as light intensity increases. Resistors
Tell series and parallel circuits apart Series: one loop, one path. Parallel: two or more branches connected across the same two points. Series and parallel circuits
State that mains electricity is ac The mains supply is an alternating current (ac) supply. Direct and alternating potential difference
Recall the UK mains frequency and pd The UK domestic supply has a frequency of 50 Hz and is about 230 V. Direct and alternating potential difference
Recall the colours of the three wires Live is brown, neutral is blue, earth is green and yellow stripes. Mains electricity
State the unit of power Power is measured in watts (W); 1 W is 1 joule per second. Power
Describe energy transfers in simple appliances e.g. a kettle transfers energy electrically from the mains to the thermal energy store of the water. Energy transfers in everyday appliances
Describe what the National Grid is A system of cables and transformers linking power stations to consumers. The National Grid
Draw particle diagrams for the three states Solid: particles touching in regular rows; liquid: particles touching but jumbled; gas: particles far apart and random. Density of materials
Name the changes of state Melting, freezing, boiling, evaporating, condensing and sublimating. Changes of state
State that heating increases the particles' energy Heating a system transfers energy to its particles, so the energy they store increases. Internal energy
Describe the motion of gas molecules They are in constant random motion, moving in all directions. Particle motion in gases
Name the three particles in an atom Protons and neutrons are in the nucleus; electrons are arranged around the nucleus. The structure of an atom
State what atomic number means The atomic number is the number of protons in the nucleus. Mass number, atomic number and isotopes
Put the models of the atom in order Tiny spheres, plum pudding, nuclear model, Bohr's energy levels, then protons and neutrons. The development of the model of the atom
Name the types of nuclear radiation Alpha particles (α), beta particles (β), gamma rays (γ) and neutrons (n). Radioactive decay and nuclear radiation
Give precautions for handling radioactive sources Use tongs, wear gloves, keep the source in a lead-lined box and spend as little time near it as possible. Radioactive contamination
Define scalar and vector quantities A scalar has magnitude only; a vector has magnitude and an associated direction. Scalar and vector quantities
Define a force as a push or pull A force acts on an object because of its interaction with another object, and is measured in newtons (N). Contact and non-contact forces
Name examples of contact forces Friction, air resistance, tension and normal contact force act when objects are touching. Contact and non-contact forces
Define weight as the force due to gravity Weight is measured in newtons (N); mass is measured in kilograms (kg). Gravity
Define resultant force A single force that has the same effect as all the original forces acting together. Resultant forces
State that work done is energy transferred When a force moves an object through a distance, energy is transferred and work is done. Work done and energy transfer
Explain why more than one force is needed To stretch, bend or compress an object, forces must act on it in different directions. Forces and elasticity
State that distance is a scalar Distance is how far an object moves; it does not involve direction. Distance and displacement
State that speed is a scalar Speed is the distance travelled per unit time and has no direction. Speed
Define velocity The velocity of an object is its speed in a given direction. Velocity
Describe motion from a distance–time graph A horizontal line means stationary; a straight sloping line means constant speed. The distance–time relationship
Recognise balanced forces on a diagram Equal-sized arrows in opposite directions mean the resultant force is zero. Newton's First Law
Define stopping distance as thinking plus braking Thinking distance is covered during the reaction time; braking distance is covered while the brakes act. Stopping distance
Recall typical reaction times Typical reaction times range from 0.2 s to 0.9 s. Reaction time
Name factors that increase braking distance Higher speed, wet or icy roads, worn brakes and worn tyres. Factors affecting braking distance 1
Give examples of transverse and longitudinal waves Transverse: ripples on water and all electromagnetic waves, such as light. Longitudinal: sound waves in air. Transverse and longitudinal waves
Label amplitude and wavelength on a diagram Amplitude: from the undisturbed position to a crest (or trough). Wavelength: one complete wave, e.g. crest to crest. Properties of waves
Name the parts of the EM spectrum in order Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays. Types of electromagnetic waves
State that EM waves are transverse EM waves are transverse waves that transfer energy from a source to an absorber. Types of electromagnetic waves
Name what substances can do to EM waves A substance can absorb, transmit, refract or reflect EM waves. Properties of electromagnetic waves 1
Name the EM waves that harm body tissue Ultraviolet, X-rays and gamma rays can have hazardous effects on human body tissue. Properties of electromagnetic waves 2
Match each EM wave to a use E.g. radio waves: television and radio; X-rays: medical imaging. Uses and applications of electromagnetic waves
State where a magnet's forces are strongest The magnetic forces are strongest at the poles: the north (seeking) pole and the south (seeking) pole. Poles of a magnet
Predict attraction or repulsion between two poles Like poles (N and N, or S and S) repel; unlike poles (N and S) attract. Poles of a magnet
Name the four magnetic materials Iron, steel, cobalt and nickel are always attracted by a magnet. Magnetic fields
State that a current produces a magnetic field When a current flows through a wire, a magnetic field is produced around the wire. Electromagnetism

Grade 4

Grade 4 checklist (PDF)

Describe the structure of a bacterial cell Cytoplasm and a cell membrane inside a cell wall, a single loop of DNA not in a nucleus, and often plasmids. Eukaryotes and prokaryotes
State the function of each structure e.g. mitochondria are where aerobic respiration happens; ribosomes are where proteins are made. Animal and plant cells
State the function of each specialised cell e.g. a nerve cell carries electrical impulses; phloem carries dissolved sugars. Cell specialisation
Say when animal and plant cells differentiate Most animal cells differentiate at an early stage; many plant cells can differentiate throughout life. Cell differentiation
Calculate the total magnification of a microscope Multiply the eyepiece lens magnification by the objective lens magnification, e.g. ×10 and ×40 give ×400. Microscopy
Compare light and electron microscopes Electron microscopes have much higher magnification and resolution; light microscopes can show living cells in colour. Microscopy
Describe what chromosomes are made of Chromosomes are made of DNA, and each chromosome carries a large number of genes. Chromosomes
State the chromosome number in human cells Body cells have 23 pairs (46 in total); sperm and egg cells have 23 single chromosomes. Chromosomes
Name the three stages of the cell cycle Growth and DNA replication; mitosis; division of the cytoplasm and cell membrane. Mitosis and the cell cycle
Name where stem cells are found In embryos, in adult bone marrow, and in the meristems of plants. Stem cells
Give examples of diffusion in living things Oxygen and carbon dioxide in gas exchange; urea from cells into the blood plasma. Diffusion
Predict the direction of water movement Water moves from the more dilute solution into the more concentrated solution. Osmosis
State where the energy comes from Active transport needs energy from respiration. Active transport
Define tissue, organ and organ system A tissue is a group of cells with a similar structure and function, an organ is a group of tissues working together, and an organ system is a group of organs working together. Principles of organisation
State what each digestive enzyme produces Amylase turns starch into sugars, proteases turn proteins into amino acids, and lipases turn lipids into fatty acids and glycerol. The human digestive system
Describe the food tests and positive results Benedict's turns from blue to brick red when heated with sugar, iodine from orange-brown to blue-black with starch, and Biuret from blue to purple with protein. The human digestive system
Label the heart's chambers and main vessels Right and left atria and ventricles, the vena cava, pulmonary artery, pulmonary vein, aorta and coronary arteries. The heart and blood vessels
State the function of each component Plasma transports dissolved substances, red blood cells carry oxygen, white blood cells defend against pathogens and platelets help the blood clot. Blood
Describe what happens in coronary heart disease Layers of fatty material build up inside the coronary arteries and narrow them. Coronary heart disease: a non-communicable disease
Tell communicable and non-communicable diseases apart Communicable diseases are caused by pathogens and can spread; non-communicable diseases cannot be passed from one person to another. Health issues
Match risk factors to the diseases they affect Diet, smoking and lack of exercise → cardiovascular disease; obesity → type 2 diabetes; alcohol → liver and brain; smoking → lung disease and lung cancer; carcinogens → cancer. The effect of lifestyle on some non-communicable diseases
Describe a benign tumour A growth of abnormal cells contained in one area, usually within a membrane, that does not invade other parts of the body. Cancer
Label a leaf cross-section From top to bottom: waxy cuticle, upper epidermis, palisade mesophyll, spongy mesophyll with air spaces and veins, lower epidermis with stomata. Plant tissues
State where meristem tissue is found At the growing tips of shoots and roots, where cells divide to make new cells. Plant tissues
Define transpiration and translocation Transpiration is the loss of water vapour from the leaves; translocation is the movement of dissolved sugars through the phloem. Plant organ system
Describe how pathogens are spread By direct contact, by water and by air, and also in food, in body fluids and by vectors. Communicable (infectious) diseases
Describe the symptoms and spread of measles Fever and a red skin rash; it is spread by breathing in droplets from coughs and sneezes. Viral diseases
Describe how HIV is spread By sexual contact or by exchange of body fluids such as blood, e.g. when drug users share needles. Viral diseases
Give the symptoms of Salmonella food poisoning Fever, abdominal cramps, vomiting and diarrhoea, caused by the bacteria and the toxins they secrete. Bacterial diseases
Give the symptoms of gonorrhoea A thick yellow or green discharge from the vagina or penis, and pain on urinating. Bacterial diseases
Describe the symptoms of rose black spot Purple or black spots develop on the leaves, which often turn yellow and drop early. Fungal diseases
State how rose black spot is spread It is spread in the environment by water (e.g. splashing rain) or by wind. Fungal diseases
Describe the main symptom of malaria Recurrent episodes of fever (the fever keeps coming back); malaria can be fatal. Protist diseases
Identify the vector of malaria Mosquitoes carry the protist and pass it to people when they bite them. Protist diseases
Describe how each defence stops pathogens Skin is a barrier; mucus traps pathogens; cilia move the mucus away; stomach acid kills pathogens. Human defence systems
Name three ways white blood cells defend Phagocytosis, producing antibodies and producing antitoxins. Human defence systems
Describe what a vaccine makes the body do It stimulates white blood cells to produce antibodies against the pathogen. Vaccination
Explain why antibiotics don't treat viral diseases Antibiotics kill bacteria but cannot kill viruses. Antibiotics and painkillers
State what new drugs are tested for Toxicity (is it harmful?), efficacy (does it work?) and dose (how much should be given?). Discovery and development of drugs
Recognise the formulae of the four substances Carbon dioxide is CO₂, water is H₂O, glucose is C₆H₁₂O₆ and oxygen is O₂. Photosynthetic reaction
Explain what a limiting factor is The factor in shortest supply, which stops the rate of photosynthesis increasing; raising it raises the rate. Rate of photosynthesis
Describe the light intensity required practical Put pondweed at different distances from a lamp and count the oxygen bubbles, or measure the volume of oxygen, in a set time. Rate of photosynthesis
State what cellulose is used for Cellulose strengthens the cell wall of plant cells. Uses of glucose from photosynthesis
Name where plants store starch and oils Starch is stored in leaves, roots and tubers such as potatoes; many seeds store oils. Uses of glucose from photosynthesis
Write the anaerobic equations for muscles and yeast In muscles: glucose → lactic acid. In plant cells and yeast: glucose → ethanol + carbon dioxide. Aerobic and anaerobic respiration
Explain why heart and breathing rates increase To supply the muscles with more oxygenated blood for the extra respiration needed to contract. Response to exercise
Give examples of metabolic reactions For example respiration, making starch, glycogen or cellulose from glucose, making lipids and proteins, and making urea. Metabolism
Name the three parts of a control system Receptors, coordination centres and effectors. Homeostasis
Name the parts of the CNS The central nervous system (CNS) is the brain and spinal cord. The human nervous system
Put the reflex arc in order Stimulus → receptor → sensory neurone → relay neurone → motor neurone → effector → response. The human nervous system
Locate the main endocrine glands Pituitary, thyroid, adrenal glands, pancreas, ovaries and testes on a body diagram. Human endocrine system
Match glands to their hormones E.g. pancreas: insulin; adrenal glands: adrenaline; testes: testosterone. Human endocrine system
Describe how insulin lowers blood glucose Insulin makes glucose move from the blood into cells; liver and muscle cells store it as glycogen. Control of blood glucose concentration
Define ovulation The release of a mature egg from an ovary, about every 28 days. Hormones in human reproduction
Explain how barrier methods work Condoms and diaphragms stop sperm reaching the egg. Contraception
Define sexual reproduction The joining (fusion) of a male gamete and a female gamete. Sexual and asexual reproduction
State how many gametes meiosis produces The cell divides twice to form four gametes. Meiosis
Describe the structure of DNA simply DNA is a polymer made up of two strands forming a double helix. DNA and the genome
Put nucleus, chromosome and gene in size order Nucleus (largest), then chromosome, then gene (a small section of DNA on a chromosome). DNA and the genome
Use genotype, phenotype, homozygous and heterozygous correctly Genotype is the alleles present, phenotype is the characteristic; homozygous means the same alleles, heterozygous different. Genetic inheritance
State which allele causes each disorder Polydactyly is caused by a dominant allele; cystic fibrosis by a recessive allele. Inherited disorders
Give the sex chromosomes of each sex Females are XX; males are XY. Sex determination
Classify causes of variation Genetic (genes inherited), environmental (conditions of development) or a combination of both. Variation
State when simple life first developed All species evolved from simple life forms that first developed more than three billion years ago. Evolution
Give examples of chosen characteristics Disease resistance in crops, more meat or milk, gentle dogs, large or unusual flowers. Selective breeding
Define genetic engineering Modifying an organism's genome by introducing a gene from another organism to give a desired characteristic. Genetic engineering
Give examples of genetic engineering Bacteria that make human insulin; crops resistant to disease, insects or herbicides; bigger, better fruits. Genetic engineering
Name two types of evidence for evolution The fossil record and the evolution of antibiotic resistance in bacteria. Evidence for evolution
Describe three ways fossils form Parts that have not decayed, parts replaced by minerals, and preserved traces such as footprints. Fossils
List the causes of extinction Environmental change, new predators, new diseases, new competitors and catastrophic events. Extinction
State ways to reduce antibiotic resistance Don't prescribe antibiotics for viral or non-serious infections, complete the course, and restrict their use in farming. Resistant bacteria
Use binomial names An organism's scientific name is its genus followed by its species, e.g. Homo sapiens. Classification of living organisms
List what plants compete for Light and space, and water and mineral ions from the soil. Communities
List what animals compete for Food, mates and territory. Communities
List the abiotic factors in the specification Light intensity, temperature, moisture level, soil pH and mineral content, wind intensity and direction, carbon dioxide (plants) and oxygen (aquatic animals). Abiotic factors
List the four biotic factors in the specification Availability of food, new predators arriving, new pathogens, and one species outcompeting another. Biotic factors
Classify adaptations as structural, behavioural or functional Structural means body features, behavioural means what it does, and functional means processes inside the body. Adaptations
State why food chains start with producers Producers (green plants and algae) make glucose by photosynthesis, so they produce the biomass for the rest of the chain. Levels of organisation
Calculate a mean, median and mode Mean = total ÷ number of values; median = middle value when in order; mode = most common value. Levels of organisation
Name the processes in the water cycle Evaporation, transpiration, condensation, precipitation, and water draining back into rivers and seas. How materials are cycled
Name human activities that reduce biodiversity For example pollution, building, farming, deforestation and destroying peat bogs. Biodiversity
Explain why more waste is produced The human population is growing rapidly and the standard of living is rising, so more resources are used. Waste management
Explain how land use reduces biodiversity Habitats are destroyed, so there is less space, food and shelter for other plants and animals. Land use
Give reasons for tropical deforestation To provide land for cattle and rice fields, and to grow crops for biofuels. Deforestation
Give human activities that increase these gases Burning fossil fuels, deforestation and destroying peat add carbon dioxide; cattle, rice fields and landfill add methane. Global warming
Name compounds from their formulae A metal with a non-metal ends in -ide (NaCl, sodium chloride); -ate means oxygen is also present (CaCO₃, calcium carbonate). Atoms, elements and compounds
Count the atoms in a formula In Ca(OH)₂ the 2 multiplies everything in the brackets: 1 Ca, 2 O and 2 H, so 5 atoms. Atoms, elements and compounds
Match each separation method to its use Filtration, crystallisation, simple distillation, fractional distillation or chromatography, depending on what is in the mixture. Mixtures
Describe filtration and crystallisation Filter off an insoluble solid; evaporate some water from a solution, then cool it so crystals of the dissolved solid form. Mixtures
Describe the plum pudding model The atom is a ball of positive charge with negative electrons embedded in it. The development of the model of the atom
Put the atomic models in order Indivisible spheres → plum pudding → nuclear model → Bohr's shells → protons → neutrons (Chadwick). The development of the model of the atom
Define atomic number The number of protons in an atom; all atoms of the same element have the same number. Relative electrical charges of subatomic particles
Define mass number The total number of protons and neutrons in an atom. Size and mass of atoms
Find protons, neutrons and electrons in atoms Protons = electrons = atomic number; neutrons = mass number − atomic number. Size and mass of atoms
Explain what relative atomic mass means An average value for the atoms of an element that takes account of the abundance of each isotope. Relative atomic mass
Write electronic structures of the first 20 elements Fill the innermost shells first, e.g. sodium (11 electrons) is 2,8,1. Electronic structure
Draw electron shell diagrams Draw circles for the shells around the nucleus and dots or crosses for the electrons. Electronic structure
State how the elements are ordered In order of atomic (proton) number. The periodic table
Describe problems with early tables They were incomplete, and strict atomic weight order put some elements in groups with the wrong properties. Development of the periodic table
Define metals by the ions they form Elements that react to form positive ions are metals; elements that do not are non-metals. Metals and non-metals
Compare physical properties of metals and non-metals Metals are usually shiny, high melting, malleable conductors; non-metals are usually dull, brittle, low melting and poor conductors. Metals and non-metals
State that noble gases are unreactive They are unreactive and do not easily form molecules; they exist as single atoms. Group 0
Describe their reactions with water They float and fizz; sodium melts into a ball; potassium's hydrogen burns with a lilac flame. Group 1
State the reactivity trend down Group 1 Reactivity increases going down the group: lithium, then sodium, then potassium. Group 1
Describe the trends down Group 7 Relative molecular mass, melting point and boiling point increase; reactivity decreases. Group 7
Choose the bond type from the elements Metal + non-metal gives ionic bonding; non-metals only give covalent bonding; metals (elements or alloys) have metallic bonding. Chemical bonds
Name the particles in each type of bond Ionic: oppositely charged ions; covalent: atoms sharing pairs of electrons; metallic: positive ions and delocalised electrons. Chemical bonds
Work out the charge from the group number Group 1 → 1+, Group 2 → 2+, Group 6 → 2−, Group 7 → 1−. Ionic bonding
Name the force holding the ions together Strong electrostatic forces of attraction between oppositely charged ions. Ionic compounds
Recognise small molecules from their formulae Formulae of a few non-metal atoms, e.g. H₂, Cl₂, HCl, H₂O, NH₃, CH₄. Covalent bonding
Describe what delocalised electrons are The outer shell electrons of metal atoms are delocalised: free to move through the whole structure. Metallic bonding
Describe particles in solids, liquids and gases Regular and vibrating in solids, close but moving around in liquids, far apart and moving quickly in gases. The three states of matter
Know that aqueous means dissolved in water Any solution in water, such as sodium chloride solution or dilute hydrochloric acid, is (aq). State symbols
State when ionic compounds conduct electricity When melted (molten) or dissolved in water, but not when solid. Properties of ionic compounds
State that small molecules don't conduct electricity The molecules have no overall electric charge. Properties of small molecules
State that polymers are solids at room temperature The forces between their large molecules are strong enough to keep them solid. Polymers
State that they have very high melting points They are solids at room temperature with very high melting and boiling points. Giant covalent structures
Define an alloy A mixture of a metal with other elements, usually other metals. Properties of metals and alloys
Name the particles that carry the charge Delocalised electrons carry electrical charge through the metal. Metals as conductors
Describe the bonding in diamond Each carbon atom forms four covalent bonds with other carbon atoms. Diamond
State the number of bonds each carbon forms Each carbon atom forms three covalent bonds with three other carbon atoms. Graphite
Describe fullerenes as hollow carbon molecules They are based on hexagonal rings of carbon atoms, sometimes with rings of five or seven atoms. Graphene and fullerenes
Name buckminsterfullerene and give its formula The first fullerene discovered: C₆₀, a hollow, spherical molecule. Graphene and fullerenes
Calculate a missing mass in a reaction Total mass of reactants = total mass of products, so subtract the known masses from the total. Conservation of mass and balanced chemical equations
Calculate M_r of a simple formula Add the A_r of every atom, e.g. CO₂ = 12 + (2 × 16) = 44. Relative formula mass
Explain a mass decrease when gas forms The gas produced escapes into the air, so its mass is no longer measured. Mass changes when a reactant or product is a gas
Find the range of a set of results Range = highest value − lowest value. Chemical measurements
Convert cm³ to dm³ Divide by 1000, e.g. 250 cm³ = 0.250 dm³. Concentration of solutions
Define oxidation and reduction using oxygen Oxidation is the gain of oxygen and reduction is the loss of oxygen. Metal oxides
Describe metal reactions with water and acid Say what you would see, e.g. fizzing, and name the products (metal hydroxide or salt, plus hydrogen). The reactivity series
State which metals carbon can extract Metals below carbon in the reactivity series, such as zinc, iron and copper, can be extracted by heating their oxides with carbon. Extraction of metals and reduction
Name the salt from the acid used Hydrochloric acid gives chlorides and sulfuric acid gives sulfates. Reactions of acids with metals
Describe the test for hydrogen A lit splint held at the mouth of the tube burns the hydrogen with a squeaky pop. Reactions of acids with metals
Predict products of acid with base or alkali acid + metal oxide or metal hydroxide → salt + water. Neutralisation of acids and salt production
Predict products of acid with a carbonate acid + metal carbonate → salt + water + carbon dioxide. Neutralisation of acids and salt production
Describe filtering and crystallising Filter off the excess solid, heat to evaporate some water, then leave the solution to cool and crystallise. Soluble salts
Measure pH with universal indicator Add the indicator and match its colour to a pH colour chart. The pH scale and neutralisation
Define an electrolyte A molten or dissolved ionic compound, which conducts electricity because its ions are free to move. The process of electrolysis
Predict products for any molten binary compound The metal forms at the cathode and the non-metal forms at the anode. Electrolysis of molten ionic compounds
State when electrolysis is used for extraction When the metal is too reactive to be extracted by carbon, or when it reacts with carbon. Using electrolysis to extract metals
State the products from sodium chloride solution Hydrogen forms at the cathode and chlorine at the anode, leaving sodium hydroxide solution. Electrolysis of aqueous solutions
Give examples of endothermic reactions Thermal decomposition and the reaction of citric acid with sodium hydrogencarbonate are endothermic. Energy transfer during exothermic and endothermic reactions
Classify a reaction from temperature data A rise in temperature means the reaction is exothermic; a fall means it is endothermic. Energy transfer during exothermic and endothermic reactions
Label the parts of a reaction profile Identify the reactants, products, activation energy and overall energy change on a given profile. Reaction profiles
Identify exothermic or endothermic from a profile Products lower than reactants means exothermic; products higher than reactants means endothermic. Reaction profiles
Calculate a mean rate of reaction Divide the quantity of reactant used or product formed by the time taken, e.g. 30 cm³ ÷ 20 s = 1.5 cm³/s. Calculating rates of reactions
Give the correct unit for rate Use g/s for a mass or cm³/s for a volume of gas, matching the units of the quantity and the time. Calculating rates of reactions
State how each factor changes the rate Increasing the concentration, pressure, surface area or temperature, or adding a catalyst, increases the rate. Factors which affect the rates of chemical reactions
Define activation energy The minimum amount of energy that particles must have to react. Collision theory and activation energy
Know that enzymes are biological catalysts Enzymes are the catalysts that speed up reactions in living things. Catalysts
Describe what a reversible reaction is The products of the reaction can react to produce the original reactants. Reversible reactions
Know the reverse has the opposite energy change If the forward reaction is exothermic, the reverse reaction is endothermic, and the other way round. Energy changes and reversible reactions
Define a closed system Apparatus that prevents the reactants and products from escaping. Equilibrium
Name the first four alkanes and their formulae Methane CH₄, ethane C₂H₆, propane C₃H₈ and butane C₄H₁₀. Crude oil, hydrocarbons and alkanes
Define a fraction A mixture of hydrocarbons with a similar number of carbon atoms, and so similar boiling points. Fractional distillation and petrochemicals
Recall how properties change with molecule size Bigger molecules: higher boiling point, higher viscosity and lower flammability. Properties of hydrocarbons
Name the two types of product Cracking produces smaller alkanes and another type of hydrocarbon called alkenes. Cracking and alkenes
Describe the bromine water test for alkenes Shake with bromine water: it turns from orange to colourless if an alkene is present. Cracking and alkenes
Contrast everyday and chemical meanings of pure In everyday language 'pure' means nothing has been added (e.g. pure milk), but the product can still be a mixture. Pure substances
Use melting points to spot pure samples A pure substance melts at a specific temperature; a mixture melts over a range of temperatures. Pure substances
Identify formulations from given information Look for a product made by mixing measured amounts of components, each with a purpose. Formulations
Match spots to known reference substances Spots of the same substance travel the same distance on the same paper with the same solvent. Chromatography
Describe the paper chromatography method Pencil start line, small spots, solvent below the line, lid on, mark the solvent front. Chromatography
Tell the hydrogen and oxygen tests apart Hydrogen: burning splint gives a pop. Oxygen: glowing splint relights. Test for hydrogen
Tell the oxygen and hydrogen tests apart Oxygen: glowing splint relights. Hydrogen: burning splint gives a pop. Test for oxygen
Name the chemical in limewater Limewater is an aqueous solution of calcium hydroxide. Test for carbon dioxide
Give a safety precaution for chlorine Chlorine is toxic, so use small amounts in a fume cupboard. Test for chlorine
Name the gases present in small proportions Carbon dioxide, water vapour and noble gases such as argon are present in small proportions. The proportions of different gases in the atmosphere
State how long the proportions have been similar The proportions of the gases have been much the same as today for about 200 million years. The proportions of different gases in the atmosphere
Name the main gas in the early atmosphere It was mainly carbon dioxide with little or no oxygen, like the atmospheres of Mars and Venus today. The Earth's early atmosphere
Describe how the oceans formed Water vapour released by volcanoes condensed to form the oceans. The Earth's early atmosphere
Write the word equation for photosynthesis carbon dioxide + water → glucose + oxygen, with light as the energy source. How oxygen increased
Name rocks and fuels that lock up carbon Sedimentary rocks such as limestone, and the fossil fuels coal, crude oil and natural gas. How carbon dioxide decreased
State why greenhouse gases are needed They keep the Earth's temperature high enough to support life. Greenhouse gases
Give two activities that release methane Farming cattle and other livestock, growing rice in paddy fields, and waste decaying in landfill sites. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Give potential effects of climate change For example, rising sea levels, more frequent and severe storms, and changes in rainfall. Global climate change
Define carbon footprint The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event. The carbon footprint and its reduction
Name the pollutants released by burning fuels Carbon dioxide, water vapour, carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates. Atmospheric pollutants from fuels
Name the gases that cause acid rain Sulfur dioxide and oxides of nitrogen cause acid rain. Properties and effects of atmospheric pollutants
Give effects of acid rain It damages buildings and statues, harms trees and plants, and makes lakes acidic, harming aquatic life. Properties and effects of atmospheric pollutants
Define finite and renewable resources A finite resource is used faster than it forms, so it will run out; a renewable resource is replaced as fast as it is used. Using the Earth's resources and sustainable development
Give natural products replaced by synthetic ones For example, wool and cotton supplemented by synthetic fibres such as polyester, or natural rubber by synthetic rubber. Using the Earth's resources and sustainable development
Explain why potable water is not pure It contains dissolved substances, whereas pure water contains only water molecules. Potable water
List the steps in treating fresh water Choose a suitable source of fresh water, pass it through filter beds, then sterilise it. Potable water
State what sewage treatment must remove Sewage and agricultural waste water need organic matter and harmful microbes removed. Waste water treatment
State what an LCA is used for To assess the environmental impact of a product over its whole life, including transport at each stage. Life cycle assessment
Name materials made from limited raw materials Metals, glass, building materials, clay ceramics and most plastics. Ways of reducing the use of resources
Name the ways energy is transferred Mechanically (a force doing work), electrically (a current doing work), by heating and by radiation such as light. Energy stores and systems
Calculate gravitational potential energy Multiply mass (kg) × gravitational field strength (N/kg) × height (m) to get the energy in joules. Changes in energy
Define specific heat capacity The amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C. Energy changes in systems
Define power Power is the rate at which energy is transferred, or the rate at which work is done. Power
Calculate power from energy and time Divide the energy transferred (J) by the time taken (s). Power
Give examples of energy being dissipated Friction heats moving parts, air resistance heats the air, and a motor makes sound. Energy transfers in a system
Calculate efficiency from energy values Divide the useful output energy by the total input energy. Efficiency
Sort resources into renewable and non-renewable Coal, oil, gas and nuclear fuel are non-renewable; all the others are renewable. National and global energy resources
Link energy resources to their uses The three main uses are transport, electricity generation and heating. National and global energy resources
Draw a simple series circuit correctly Use a ruler, straight wires and the correct symbols, with no gaps in the loop. Standard circuit diagram symbols
Recognise diode, LED, fuse and variable resistor Tell apart symbols that look alike, such as the diode and the LED, or the resistor and the fuse. Standard circuit diagram symbols
State what a circuit needs for current A closed circuit (complete loop) that includes a source of potential difference, such as a cell. Electrical charge and current
Calculate charge using Q = I t Multiply the current in amps by the time in seconds to get the charge in coulombs. Electrical charge and current
Describe how resistance affects current For a given potential difference, the greater the resistance, the smaller the current. Current, resistance and potential difference
Calculate pd using V = I R Multiply the current in amps by the resistance in ohms to get the pd in volts. Current, resistance and potential difference
Recall that a thermistor's resistance falls when hot The resistance of a thermistor decreases as temperature increases. Resistors
State the series and parallel rules Series: same current, pd shared. Parallel: same pd across each branch, branch currents add up. Series and parallel circuits
Add resistances in series Use R_total = R₁ + R₂. Series and parallel circuits
Name a source of direct pd Cells and batteries supply a direct potential difference. Direct and alternating potential difference
State the job of each wire Live carries the alternating pd from the supply, neutral completes the circuit, earth is a safety wire. Mains electricity
Explain what power means Power is the rate of energy transfer: the energy transferred each second. Power
Calculate power using P = V I Multiply the pd in volts by the current in amps to get the power in watts. Power
State what affects the energy transferred The power of the appliance and how long it is switched on for. Energy transfers in everyday appliances
Calculate energy using E = P t Power in watts × time in seconds gives energy in joules. Energy transfers in everyday appliances
State what a step-up transformer does It increases the potential difference from the power station to the transmission cables. The National Grid
State what a step-down transformer does It decreases the potential difference to a much lower value for domestic use. The National Grid
Recall and use density = mass ÷ volume Substitute into ρ = m / V with mass in kg and volume in m³ to get a density in kg/m³. Density of materials
State that mass is conserved When a substance changes state the number of particles stays the same, so its mass does not change. Changes of state
Define internal energy The total kinetic energy and potential energy of all the particles (atoms and molecules) that make up a system. Internal energy
Define specific heat capacity The amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C. Temperature changes in a system and specific heat capacity
Substitute into ΔE = m c Δθ Calculate the change in thermal energy with m in kg, c in J/kg °C and Δθ in °C. Temperature changes in a system and specific heat capacity
Know temperature stays constant during state changes While a substance melts, boils, freezes or condenses, its temperature does not change. Changes of state and specific latent heat
Link gas temperature to molecules' kinetic energy The higher the temperature, the greater the average kinetic energy of the molecules, so the faster they move on average. Particle motion in gases
Give the relative charge of each particle Proton +1, neutron 0, electron −1, so the nucleus is positively charged. The structure of an atom
Recall the size of an atom The radius of an atom is about 1 × 10⁻¹⁰ m. The structure of an atom
State what mass number means The mass number is the total number of protons and neutrons in the nucleus. Mass number, atomic number and isotopes
Explain why atoms have no overall charge An atom has equal numbers of protons and electrons, and their charges are equal and opposite. Mass number, atomic number and isotopes
Describe the plum pudding model The atom is a ball of positive charge with negative electrons embedded in it. The development of the model of the atom
Define radioactive decay and activity Unstable nuclei give out radiation to become more stable; activity is decays per second, in becquerels (Bq). Radioactive decay and nuclear radiation
State what absorbs each radiation Alpha: paper; beta: a few mm of aluminium; gamma: reduced by thick lead or concrete. Radioactive decay and nuclear radiation
Recall the symbols for alpha and beta Alpha is \({}^{4}_{2}\mathrm{He}\) and beta is \({}^{0}_{-1}\mathrm{e}\). Nuclear equations
Define half-life The time for the number of unstable nuclei in a sample, or its count rate, to halve. Half-lives and the random nature of radioactive decay
Define contamination and irradiation Contamination: unwanted radioactive material on or in something; irradiation: exposure to radiation from outside. Radioactive contamination
Sort common quantities into scalars and vectors Distance, speed, mass, time, energy and temperature are scalars; displacement, velocity, acceleration, force and momentum are vectors. Scalar and vector quantities
Name examples of non-contact forces Gravitational, electrostatic and magnetic forces act even when the objects are physically separated. Contact and non-contact forces
Calculate weight using W = m g For example, 60 kg × 9.8 N/kg = 588 N. Gravity
Find the resultant of forces along a line Add forces acting in the same direction; subtract forces acting in opposite directions. Resultant forces
Calculate work done using W = F s For example, 50 N × 3.0 m = 150 J. Work done and energy transfer
Distinguish elastic and inelastic deformation An elastically deformed object returns to its original shape when the forces are removed; an inelastically deformed one does not. Forces and elasticity
State that displacement is a vector Displacement is the straight-line distance from the start point to the finish point, with the direction of that line. Distance and displacement
Calculate distance using s = v t For example, 1.5 m/s for 60 s gives 90 m. Speed
Recall typical speeds of everyday motion Walking ~1.5 m/s, running ~3 m/s, cycling ~6 m/s, sound in air ~330 m/s. Speed
Explain the difference between speed and velocity Speed is a scalar (magnitude only); velocity is a vector (magnitude and direction). Velocity
Plot a distance–time graph from data Time on the x-axis, distance on the y-axis, labelled axes with units and sensible scales. The distance–time relationship
Calculate acceleration using a = Δv ÷ t From 4 m/s to 16 m/s in 3 s: a = 12 ÷ 3 = 4 m/s². Acceleration
Describe motion from a velocity–time graph Horizontal line: constant velocity; sloping up: accelerating; sloping down: decelerating. Acceleration
State Newton's First Law If the resultant force on an object is zero, it stays at rest or keeps moving at the same velocity. Newton's First Law
Find a force from steady motion At a steady speed in a straight line, the driving force equals the total resistive force. Newton's First Law
Calculate force using F = m a For example, 1200 kg × 2.5 m/s² = 3000 N. Newton's Second Law
State Newton's Third Law Whenever two objects interact, the forces they exert on each other are equal and opposite. Newton's Third Law
Calculate stopping distance from given data Add the thinking distance and the braking distance. Stopping distance
List factors that increase reaction time Tiredness, drugs, alcohol and distractions (e.g. using a phone). Reaction time
Explain how wet or icy roads affect braking There is less friction between the tyres and the road, so the braking distance is longer. Factors affecting braking distance 1
Describe the energy transfer when a vehicle brakes Energy is transferred from the kinetic store of the vehicle to the thermal store of the brakes. Factors affecting braking distance 2
State what waves transfer Waves transfer energy (and can carry information) from place to place, but they do not transfer matter. Transverse and longitudinal waves
Define frequency and period Frequency is the number of waves passing a point each second (Hz); the period is the time for one wave (s). Properties of waves
Calculate wave speed using v = f λ Multiply the frequency in Hz by the wavelength in m to get the wave speed in m/s. Properties of waves
Link spectrum position to wavelength and frequency Radio waves have the longest wavelength and lowest frequency; gamma rays have the shortest wavelength and highest frequency. Types of electromagnetic waves
State what causes refraction Refraction happens because the wave changes speed when it enters a different substance. Properties of electromagnetic waves 1
State the effects of ultraviolet on skin Ultraviolet can make skin age prematurely and increases the risk of skin cancer. Properties of electromagnetic waves 2
Give two uses of microwaves Satellite communications and cooking food. Uses and applications of electromagnetic waves
Give three uses of infrared Electrical heaters, cooking food and infrared cameras. Uses and applications of electromagnetic waves
Identify magnetic forces as non-contact forces Magnets attract or repel each other without touching, so these are non-contact forces. Poles of a magnet
Draw the field pattern of a bar magnet Curved lines from the north pole to the south pole, with arrows, closest together at the poles. Magnetic fields
Describe how to show a wire's magnetic field Put plotting compasses around a vertical wire: they line up in a circle when the current is switched on. Electromagnetism
State what the motor effect is A wire carrying a current in a magnetic field has a force on it, and so does the magnet. Fleming's left-hand rule (HT only)
State that a coil carrying current rotates A coil of wire carrying a current in a magnetic field tends to rotate. Electric motors (HT only)

Grade 5

Grade 5 checklist (PDF)

Compare prokaryotic and eukaryotic cells Say what both have (cell membrane, cytoplasm, ribosomes) and how they differ, above all whether the DNA is enclosed in a nucleus. Eukaryotes and prokaryotes
Convert between mm, µm and nm Multiply by 1000 for each step down (mm → µm → nm) and divide by 1000 for each step up. Eukaryotes and prokaryotes
Explain why some plant cells lack chloroplasts Cells that receive no light, such as root cells, cannot photosynthesise, so they have no chloroplasts. Animal and plant cells
Describe the adaptations of each specialised cell e.g. a sperm cell has a tail, many mitochondria and enzymes in its head. Cell specialisation
State what cell division does in adults In mature animals, cell division is mainly for repair and replacement. Cell differentiation
Use magnification = image size ÷ real size Rearrange the equation to find the magnification, the image size or the real size. Microscopy
Prepare a slide and focus a microscope Thin sample, stain, coverslip; start on the lowest power and focus with the coarse, then the fine, focus. Microscopy
Put cell, nucleus, chromosome and gene in order Largest to smallest: cell, nucleus, chromosome, gene. Chromosomes
Describe what happens in each stage The cell grows, copies its sub-cellular structures and DNA, divides its nucleus, then splits in two. Mitosis and the cell cycle
State why mitosis is important For the growth and development of multicellular organisms, and to repair and replace cells. Mitosis and the cell cycle
Recognise where mitosis is happening e.g. a root tip growing, a cut healing, an embryo developing. Mitosis and the cell cycle
Compare embryonic and adult stem cells Embryonic stem cells can become most types of human cell; adult bone marrow stem cells form fewer types, including blood cells. Stem cells
Describe uses of meristem cloning Making clones quickly and cheaply, saving rare species, and producing crops with useful features. Stem cells
Explain the factors that affect the rate A bigger concentration gradient, a higher temperature and a larger surface area all increase the rate of diffusion. Diffusion
Describe the osmosis required practical Weigh pieces of plant tissue, leave them in a range of concentrations, then reweigh them. Osmosis
Calculate percentage change in mass Change in mass ÷ starting mass × 100; a loss in mass gives a negative answer. Osmosis
Describe two examples of active transport Mineral ions from the soil into root hair cells; sugar from the gut into the blood. Active transport
Classify a structure by its level For example, a red blood cell is a cell, blood is a tissue, the heart is an organ and the circulatory system is an organ system. Principles of organisation
Recall where each digestive enzyme is made Amylase in the salivary glands, pancreas and small intestine; proteases in the stomach, pancreas and small intestine; lipases in the pancreas and small intestine. The human digestive system
Describe the double circulatory system The right ventricle pumps blood to the lungs and the left ventricle pumps blood around the rest of the body. The heart and blood vessels
Describe the role of the pacemaker A group of cells in the right atrium controls the natural resting heart rate; an artificial pacemaker is an electrical device that corrects an irregular heart rate. The heart and blood vessels
Identify blood cells in a photo or diagram Red blood cells are biconcave discs with no nucleus, white blood cells are larger with a nucleus, and platelets are tiny fragments. Blood
List substances transported by the plasma Carbon dioxide, urea, soluble products of digestion such as glucose and amino acids, hormones and antibodies. Blood
Describe how stents and statins treat CHD A stent holds the coronary artery open; statins lower blood cholesterol, which slows the build-up of fatty material. Coronary heart disease: a non-communicable disease
Describe treatments for faulty valves and heart failure Faulty valves are replaced with biological or mechanical valves; heart failure can be treated with a donor heart (or heart and lungs) or, occasionally, an artificial heart. Coronary heart disease: a non-communicable disease
Give factors other than disease affecting health Diet, stress and life situations can have a big effect on both physical and mental health. Health issues
Describe effects of smoking and alcohol in pregnancy Both can harm the unborn baby, e.g. smoking can cause low birth weight and alcohol can damage the baby's brain development. The effect of lifestyle on some non-communicable diseases
Describe malignant tumours and secondary tumours Malignant tumour cells are cancers: they invade neighbouring tissues and spread in the blood to form secondary tumours. Cancer
Give lifestyle risk factors for cancer For example smoking (lung cancer), obesity (e.g. bowel cancer), too much UV light (skin cancer) and some viral infections (e.g. cervical cancer). Cancer
State the function of each leaf tissue Epidermis covers the leaf, palisade does most photosynthesis, spongy mesophyll lets gases diffuse, xylem carries water and phloem carries sugars. Plant tissues
Describe how root hair cells absorb substances They take up water by osmosis and mineral ions by active transport, helped by their large surface area. Plant organ system
Compare the structure of xylem and phloem Xylem is hollow tubes strengthened by lignin; phloem is tubes of elongated cells with pores in the end walls. Plant organ system
Explain how bacteria and viruses make you ill Both reproduce rapidly in the body; bacteria release toxins that damage tissues, and viruses reproduce inside cells and damage them. Communicable (infectious) diseases
Describe ways to reduce the spread of disease Hygiene, isolating infected individuals, destroying or controlling vectors, and vaccination. Communicable (infectious) diseases
Describe how measles and HIV are controlled Measles: vaccinating young children; HIV: condoms, not sharing needles and antiretroviral drugs. Viral diseases
Describe how each disease is spread Salmonella: bacteria swallowed in food or on food prepared in unhygienic conditions; gonorrhoea: sexual contact. Bacterial diseases
Describe how the spread of each is controlled Vaccinating poultry and hygienic food preparation for Salmonella; antibiotics and condoms for gonorrhoea. Bacterial diseases
Describe how rose black spot is treated Use fungicides and/or remove and destroy the affected leaves. Fungal diseases
Describe how the spread of malaria is controlled Stop mosquitoes breeding, and use mosquito nets to avoid being bitten. Protist diseases
Describe phagocytosis A white blood cell engulfs a pathogen and digests it. Human defence systems
Explain how vaccination prevents illness If the live pathogen enters later, white blood cells quickly make the correct antibodies and destroy it before it causes illness. Vaccination
Explain why specific antibiotics are needed Different antibiotics kill different bacteria, so the antibiotic must match the bacterium causing the disease. Antibiotics and painkillers
Describe preclinical testing The drug is tested in a laboratory on cells, tissues and live animals before any people take it. Discovery and development of drugs
Describe the stages of clinical trials Very low doses are given first to check safety; further trials on patients find the optimum dose. Discovery and development of drugs
Explain why photosynthesis is endothermic Energy is transferred from the environment to the chloroplasts by light, so the reaction takes in energy. Photosynthetic reaction
State where the reactants come from Carbon dioxide diffuses into the leaf from the air through the stomata; water is absorbed by the roots and carried up in the xylem. Photosynthetic reaction
Explain the effect of temperature The rate rises up to an optimum temperature, then falls quickly because the enzymes that control photosynthesis denature. Rate of photosynthesis
Explain a one-factor rate graph Where the line rises the factor on the x-axis is limiting; where it levels off another factor has become limiting. Rate of photosynthesis
Describe how glucose reaches storage organs Sugars made in the leaves are carried in solution in the phloem to where they are used or stored. Uses of glucose from photosynthesis
Describe respiration as a continuous exothermic reaction It happens all the time in living cells and transfers energy to the surroundings, supplying the energy for living processes. Aerobic and anaerobic respiration
Describe fermentation and its uses Anaerobic respiration in yeast makes ethanol and carbon dioxide, which are used to make alcoholic drinks and bread. Aerobic and anaerobic respiration
Explain when muscles respire anaerobically When oxygen cannot be supplied fast enough for aerobic respiration alone, as in vigorous exercise. Response to exercise
Calculate changes from exercise data Work out increases, percentage changes and recovery times from tables and graphs of heart rate or breathing rate. Response to exercise
Name the building blocks of large molecules Carbohydrates are made from sugars, proteins from amino acids, and lipids from glycerol and fatty acids. Metabolism
State how a lipid molecule forms One molecule of glycerol joins with three molecules of fatty acids. Metabolism
Explain why homeostasis is important It keeps conditions at the optimum for enzyme action and all cell functions. Homeostasis
Describe the job of each part Receptors detect stimuli, coordination centres process the information, and effectors (muscles or glands) bring about a response. Homeostasis
Explain why reflex actions are fast They are automatic and do not involve the conscious part of the brain. The human nervous system
Describe the ruler-drop reaction time practical Catch a dropped ruler, record the distance it fell and convert it to a reaction time. The human nervous system
Compare hormonal and nervous control Hormones travel in the blood and are slower but longer-lasting; nerve impulses are fast and short-lived. Human endocrine system
Compare the causes of Type 1 and 2 Type 1: the pancreas does not make enough insulin. Type 2: body cells stop responding to insulin. Control of blood glucose concentration
Describe treatments for each type of diabetes Type 1: insulin injections. Type 2: a carbohydrate-controlled diet and an exercise regime. Control of blood glucose concentration
State the roles of the four cycle hormones FSH matures an egg, LH triggers its release, and oestrogen and progesterone maintain the uterus lining. Hormones in human reproduction
Explain how hormonal methods work The pill inhibits FSH so no eggs mature; progesterone implants stop eggs maturing and being released. Contraception
Describe how IUDs and spermicides work IUDs prevent an embryo implanting or release a hormone; spermicides kill or disable sperm. Contraception
Name the hormones in fertility drugs FSH and LH. The use of hormones to treat infertility (HT only)
Describe how a fertility drug works FSH and LH make eggs mature and be released, so the woman may become pregnant in the normal way. The use of hormones to treat infertility (HT only)
State the effects of adrenaline It increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles. Feedback systems (HT only)
State the role of thyroxine It stimulates the basal metabolic rate and is important in growth and development. Feedback systems (HT only)
Name the cell division each type uses Gametes are made by meiosis; asexual reproduction involves only mitosis. Sexual and asexual reproduction
Describe what happens in meiosis The genetic information is copied, then the cell divides twice to give four genetically different gametes, each with a single set of chromosomes. Meiosis
Give chromosome numbers in body cells and gametes A human body cell has 46 chromosomes (23 pairs) and a human gamete has 23. Meiosis
Define gene and genome A gene is a small section of DNA on a chromosome; the genome is all of an organism's genetic material. DNA and the genome
Complete a Punnett square Put each parent's gametes on the outside and combine one allele from each in every box. Genetic inheritance
Give cross outcomes as ratios or probabilities For example 3 : 1, or a probability of 0.25, 25%, ¼ or 1 in 4. Genetic inheritance
Explain what a carrier is A heterozygous person with one recessive allele who does not have the disorder but can pass it on. Inherited disorders
State what the other 22 pairs do 22 pairs control characteristics only; one pair carries the genes that determine sex. Sex determination
Draw a genetic cross for sex XX × XY in a Punnett square gives XX, XX, XY, XY. Sex determination
Give examples of each cause Blood group is genetic, a scar is environmental, and body mass depends on both. Variation
State that populations show genetic variation There is usually extensive genetic variation within a population of a species. Variation
List the steps of natural selection Variation, competition, the best suited survive and reproduce, alleles passed on, alleles become more common. Evolution
Describe the steps of selective breeding Choose parents with the characteristic, breed them, select the best offspring, and repeat over many generations. Selective breeding
State what GM crops are Crops whose genes have been modified by genetic engineering; they generally give increased yields. Genetic engineering
Explain why genes support Darwin's theory It has been shown that characteristics are passed on to offspring in genes, which explains how they are inherited. Evidence for evolution
Explain why some remains do not decay One or more of the conditions needed for decay (such as oxygen, warmth or moisture) are absent. Fossils
Give examples of catastrophic events Massive volcanic eruptions or collisions with asteroids. Extinction
Explain why bacteria evolve rapidly They reproduce at a fast rate, so there are many generations in a short time. Resistant bacteria
Describe how Linnaeus classified organisms Into groups depending on their structure and characteristics. Classification of living organisms
Name the three domains Archaea, bacteria and eukaryota. Classification of living organisms
Explain what interdependence means Each species depends on others for food, shelter, pollination or seed dispersal, so removing one species can affect the whole community. Communities
Describe a trend in abiotic data State how one variable changes as the other changes, quoting values from the table or graph. Abiotic factors
Explain the effect of food availability More food means more organisms survive and breed, so the population grows; less food has the opposite effect. Biotic factors
Define an extremophile and give an example An organism that lives in extreme conditions of temperature, pressure or salt concentration, e.g. bacteria in deep sea vents. Adaptations
Describe using quadrats to estimate population size Place quadrats randomly, count the organisms, find the mean per quadrat, then scale up to the whole area. Levels of organisation
Name processes that add or remove carbon dioxide Photosynthesis removes carbon dioxide from the air; respiration and combustion release it. How materials are cycled
Explain why biodiversity matters to humans The future of humans relies on it, e.g. for food, materials, medicines and stable ecosystems. Biodiversity
Explain how pollution reduces biodiversity Pollution kills plants and animals, so fewer species survive in the area. Waste management
State why peat bogs are destroyed Peat is dug up to produce garden compost. Land use
Explain how deforestation reduces biodiversity Forest habitats are destroyed and replaced by grazing land or one crop, so many species are lost. Deforestation
Describe biological consequences of global warming Habitat loss as sea levels rise, changes in distribution and migration, and loss of biodiversity. Global warming
Explain how each programme helps biodiversity Say what the programme does and which species or habitats it protects. Maintaining biodiversity
Write word equations for reactions Reactants on the left, products on the right, joined by an arrow, e.g. magnesium + oxygen → magnesium oxide. Atoms, elements and compounds
Describe simple distillation The solvent boils off, is cooled and condensed in a condenser, and is collected, leaving the dissolved solid behind. Mixtures
Describe fractional distillation Liquids with different boiling points are separated using a fractionating column; the lowest boiling point liquid is collected first. Mixtures
Describe the nuclear model A tiny, positively charged nucleus that contains almost all the mass, with electrons outside it. The development of the model of the atom
Explain why atoms have no overall charge The number of electrons equals the number of protons, so the charges cancel. Relative electrical charges of subatomic particles
Identify an element from its proton number Different elements have different numbers of protons, so the atomic number tells you the element. Relative electrical charges of subatomic particles
Define isotopes Atoms of the same element with different numbers of neutrons: same atomic number, different mass number. Size and mass of atoms
Recall the sizes of atoms and nuclei Atom radius about 0.1 nm (1 × 10⁻¹⁰ m); nucleus radius less than 1/10 000 of that (about 1 × 10⁻¹⁴ m). Size and mass of atoms
Calculate A_r for two isotopes Multiply each mass number by its percentage abundance, add the results, then divide by 100. Relative atomic mass
Explain why A_r is rarely whole It is an average of isotopes with different mass numbers, weighted by how common each one is. Relative atomic mass
Link electronic structure to group and period Outer electrons = group number (Groups 1 to 7); number of occupied shells = period. Electronic structure
Identify an element from its electronic structure Add up the electrons to get the atomic number, e.g. 2,8,5 is 15, which is phosphorus. Electronic structure
Explain why group members react similarly They have the same number of electrons in their outer shell. The periodic table
Link position to electronic structure Group number = outer electrons (Groups 1 to 7); period = number of occupied shells. The periodic table
Describe what Mendeleev did He left gaps for undiscovered elements and changed the order of some elements to fit their properties. Development of the periodic table
Compare the oxides of metals and non-metals Metal oxides are basic; non-metal oxides are usually acidic. Metals and non-metals
Explain their unreactivity using electrons Their atoms have stable arrangements of electrons: a full outer shell of 8 (2 for helium). Group 0
Describe the boiling point trend Boiling points increase going down the group, as relative atomic mass increases. Group 0
Write equations for their reactions With water, oxygen and chlorine, e.g. 2K + 2H₂O → 2KOH + H₂. Group 1
Describe the compounds halogens form Ionic compounds with metals (halide ions, 1−); covalent molecules with non-metals, e.g. HCl. Group 7
Predict whether a displacement reaction happens A more reactive halogen displaces a less reactive one from a solution of its salt. Group 7
Decide the bond type from a formula Use the periodic table to decide whether each element in, for example, KBr, SO₂ or Zn is a metal or a non-metal. Chemical bonds
Write the electronic structure of an ion For example, Na (2,8,1) becomes Na⁺ (2,8) and O (2,6) becomes O²⁻ (2,8). Ionic bonding
Draw dot and cross diagrams for ionic compounds Show each ion in square brackets with its charge, using dots and crosses for electrons from different atoms. Ionic bonding
State that the forces act in all directions Each ion is attracted to all the oppositely charged ions around it, throughout the lattice. Ionic compounds
Recognise an ionic structure from a diagram Look for a regular lattice of two types of ion, often labelled with charges, and no separate molecules. Ionic compounds
Draw dot and cross diagrams for simple molecules Hydrogen, chlorine, hydrogen chloride, water, ammonia and methane, which have single bonds only. Covalent bonding
Describe the metallic bond Strong electrostatic attraction between positive metal ions and the shared delocalised electrons. Metallic bonding
Predict states from melting and boiling points Below the melting point: solid; between the melting and boiling points: liquid; above the boiling point: gas. The three states of matter
Add state symbols to a simple equation For example, Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). State symbols
Explain high melting points using electrostatic forces A lot of energy is needed to overcome the many strong electrostatic forces between oppositely charged ions. Properties of ionic compounds
Explain low boiling points using intermolecular forces Only weak intermolecular forces must be overcome, which needs little energy. Properties of small molecules
Describe the bonds in a polymer chain The atoms in each chain are linked to each other by strong covalent bonds. Polymers
Recognise a polymer from a diagram Look for a repeating unit in brackets with bonds through the brackets and n after them. Polymers
Explain their very high melting points Many strong covalent bonds must be broken, which needs a lot of energy. Giant covalent structures
Explain why most metals have high melting points Giant structures with strong metallic bonding need a lot of energy to overcome. Properties of metals and alloys
Explain why pure metals are soft The layers of atoms can slide over each other easily. Properties of metals and alloys
Explain electrical conduction in metals The delocalised electrons are free to move through the structure, carrying charge. Metals as conductors
Explain why diamond is very hard Many strong covalent bonds hold the atoms rigidly in a 3D network. Diamond
Explain diamond's very high melting point A lot of energy is needed to break the many strong covalent bonds. Diamond
Explain why graphite is soft and slippery There are no covalent bonds between the layers, so the layers can slide over each other. Graphite
Give uses of fullerenes and nanotubes Fullerenes: drug delivery, lubricants, catalysts; nanotubes: nanotechnology, electronics and strengthening materials. Graphene and fullerenes
Balance a symbol equation Change only the big numbers in front of formulae until every element has the same number of atoms on both sides. Conservation of mass and balanced chemical equations
Calculate M_r for formulae with brackets Multiply everything inside the bracket, e.g. Ca(OH)₂ = 40 + 2 × (16 + 1) = 74. Relative formula mass
Explain why a heated metal gains mass Oxygen atoms from the air combine with the metal, so the metal oxide has a greater mass than the metal. Mass changes when a reactant or product is a gas
Identify an anomalous result A result that clearly does not fit the pattern of the others; leave it out of the mean. Chemical measurements
State what one mole contains One mole of any substance contains 6.02 × 10²³ particles (the Avogadro constant). Moles (HT only)
Recall the mass of one mole The mass of one mole in grams equals the A_r or M_r, e.g. 1 mol of H₂O has a mass of 18 g. Moles (HT only)
Read mole ratios from a balanced equation The balancing numbers give moles, e.g. 2H₂ + O₂ → 2H₂O means 2 mol of H₂ react with 1 mol of O₂. Amounts of substances in equations (HT only)
Define limiting reactant and excess The limiting reactant is completely used up; the reactant in excess is partly left over. Limiting reactants (HT only)
Calculate concentration in g/dm³ Concentration = mass of solute (g) ÷ volume of solution (dm³). Concentration of solutions
Identify what is oxidised or reduced In an equation, the substance that gains oxygen is oxidised and the substance that loses oxygen is reduced. Metal oxides
Deduce an order of reactivity from results The more vigorous the reaction (more bubbles, bigger temperature rise), the more reactive the metal. The reactivity series
Predict whether a displacement reaction happens A metal displaces another metal from its compound only if it is more reactive. The reactivity series
Write equations for reduction with carbon For example, 2ZnO + C → 2Zn + CO₂. Extraction of metals and reduction
Define oxidation and reduction using electrons Oxidation is the loss of electrons and reduction is the gain of electrons (OIL RIG). Oxidation and reduction in terms of electrons (HT only)
Tell the difference between bases and alkalis A base neutralises an acid; an alkali is a base that dissolves in water, such as a soluble metal hydroxide. Neutralisation of acids and salt production
Explain why excess solid is added Excess solid makes sure all the acid reacts, so the salt solution contains no leftover acid. Soluble salts
Tell when the solid is in excess Solid stays undissolved at the bottom, and for a carbonate the fizzing stops. Soluble salts
Name the ions in acids and alkalis Acids produce H⁺ ions in water and alkalis produce OH⁻ ions in water. The pH scale and neutralisation
Compare universal indicator with a pH probe A pH probe gives a more precise numerical reading; universal indicator gives an approximate value from a colour. The pH scale and neutralisation
Describe the pH change during neutralisation As alkali is added to acid, the pH rises to 7 at neutralisation and above 7 when alkali is in excess. The pH scale and neutralisation
Name examples of strong and weak acids Strong: hydrochloric, nitric and sulfuric acids. Weak: ethanoic, citric and carbonic acids. Strong and weak acids (HT only)
Predict which electrode each ion moves to Positive ions move to the cathode and negative ions move to the anode. The process of electrolysis
Describe what is seen at each electrode For lead bromide, silvery lead forms at the cathode and brown bromine vapour at the anode. Electrolysis of molten ionic compounds
Name the products from aluminium oxide Aluminium forms at the cathode and oxygen forms at the anode. Using electrolysis to extract metals
Explain why electrolysis is expensive Large amounts of energy are needed to melt the compound and to produce the electric current. Using electrolysis to extract metals
Predict the product at the cathode Hydrogen forms if the metal is more reactive than hydrogen; otherwise the metal forms. Electrolysis of aqueous solutions
Predict the product at the anode The halogen forms if halide ions are present; otherwise oxygen forms. Electrolysis of aqueous solutions
State where oxidation and reduction happen Reduction (gain of electrons) happens at the cathode; oxidation (loss of electrons) happens at the anode. Representation of reactions at electrodes as half equations (HT only)
Explain energy conservation in a reaction Energy is not created or destroyed, so in an exothermic reaction the products have less energy than the reactants by the amount transferred. Energy transfer during exothermic and endothermic reactions
Read energy values from a profile Activation energy = peak − reactants; overall energy change = products − reactants. Reaction profiles
State energy changes in breaking and making bonds Breaking bonds needs energy to be supplied; making bonds releases energy. The energy change of reactions (HT only)
Interpret graphs of product formed against time The steeper the curve, the faster the rate; a horizontal line means the reaction has stopped. Calculating rates of reactions
Describe the gas-volume method for rates Measure the volume of gas given off at regular time intervals with a gas syringe or an upturned measuring cylinder. Factors which affect the rates of chemical reactions
Describe the disappearing-cross (turbidity) method Time how long it takes for a cross under the flask to disappear as a cloudy precipitate forms. Factors which affect the rates of chemical reactions
Explain concentration and pressure effects There are more particles in the same volume, so collisions are more frequent. Collision theory and activation energy
Explain the effect of surface area More particles of the solid are exposed to the other reactant, so collisions are more frequent. Collision theory and activation energy
Identify a catalyst from experimental data It speeds up the reaction, has the same mass at the end and is not in the equation. Catalysts
Describe heating and cooling ammonium chloride Heating decomposes it into ammonia and hydrogen chloride; cooling makes these gases re-form the white solid. Reversible reactions
Write equations for reversible reactions Use ⇌ in word and balanced symbol equations, e.g. NH₄Cl ⇌ NH₃ + HCl. Reversible reactions
State that equal energy is transferred each way The energy taken in one way is exactly the same as the energy given out the other way. Energy changes and reversible reactions
Describe the copper sulfate reversible reaction Heating blue hydrated copper sulfate gives white anhydrous copper sulfate and water; adding water reverses it. Energy changes and reversible reactions
State when equilibrium is reached When the forward and reverse reactions happen at exactly the same rate. Equilibrium
Know that amounts stay constant at equilibrium The concentrations of reactants and products stop changing, but they are not necessarily equal. Equilibrium
State Le Chatelier's principle If a condition of a system at equilibrium is changed, the system responds to counteract the change. The effect of changing conditions on equilibrium (HT only)
Predict the effect of adding more reactant More products are formed until equilibrium is reached again. The effect of changing concentration (HT only)
Predict heating an exothermic reaction Raising the temperature decreases the relative amount of products at equilibrium. The effect of temperature changes on equilibrium (HT only)
Count the molecules on each side Add the numbers in front of each gas formula in the balanced equation (no number means 1). The effect of pressure changes on equilibrium (HT only)
Use the general formula of the alkanes Recognise an alkane from its formula, and write the formula for any number of carbon atoms: 10 carbon atoms gives C₁₀H₂₂. Crude oil, hydrocarbons and alkanes
Draw the displayed formula of an alkane Show every atom and every bond: each carbon atom forms four single bonds and each hydrogen atom forms one. Crude oil, hydrocarbons and alkanes
Describe the temperature gradient in the column The fractionating column is hottest at the bottom and coolest at the top. Fractional distillation and petrochemicals
Explain what feedstock means A raw material used to make other chemicals; fractions are feedstock for the petrochemical industry. Fractional distillation and petrochemicals
Choose a suitable fuel using property data For example, a fuel for a gas stove must have a boiling point below room temperature and be very flammable. Properties of hydrocarbons
State what happens to the fuel in combustion The carbon and hydrogen in the fuel are oxidised, and energy is released. Properties of hydrocarbons
Describe the conditions for catalytic and steam cracking Catalytic: vapour passed over a hot catalyst. Steam: vapour mixed with steam and heated to a very high temperature. Cracking and alkenes
Give uses of the products of cracking Smaller alkanes are used as fuels such as petrol; alkenes are used to make polymers and many other chemicals. Cracking and alkenes
Describe how impurities change melting and boiling Impurities lower the melting point and widen the melting range; dissolved impurities raise the boiling point. Pure substances
Interpret heating curves to judge purity A flat section at a fixed temperature shows a pure substance changing state; a sloping section shows a mixture. Pure substances
Explain why quantities are carefully measured The right amount of each component gives the product the properties it needs. Formulations
Suggest the purpose of a component Use the information given, e.g. a pigment gives colour and a sweetener improves taste. Formulations
Calculate an Rf value Rf = distance moved by substance ÷ distance moved by solvent, both measured from the start line. Chromatography
Name reactions that produce hydrogen Metals with acids, very reactive metals with water, and electrolysis of many solutions (at the negative electrode). Test for hydrogen
Name reactions that produce oxygen Decomposition of hydrogen peroxide, electrolysis (at the positive electrode) and photosynthesis. Test for oxygen
Describe how to test gas from a reaction Use a delivery tube to bubble the gas from the reaction through limewater. Test for carbon dioxide
Name reactions that produce carbon dioxide Acids with metal carbonates, and complete combustion of fuels that contain carbon. Test for carbon dioxide
Name a reaction that produces chlorine Electrolysis of a chloride solution, such as sodium chloride solution: chlorine forms at the positive electrode. Test for chlorine
Calculate the volume of a gas in air Multiply the total volume by the percentage divided by 100, e.g. 20 ÷ 100 × 500 cm³ = 100 cm³ of oxygen. The proportions of different gases in the atmosphere
Name other gases in the early atmosphere Nitrogen from volcanoes gradually built up, and there may have been small proportions of methane and ammonia. The Earth's early atmosphere
State when algae first produced oxygen Algae first produced oxygen about 2.7 billion years ago, and oxygen appeared in the atmosphere soon after. How oxygen increased
Describe how limestone formed Shells and skeletons of sea creatures, made of calcium carbonate, settled, were buried and were compressed into rock. How carbon dioxide decreased
Describe how coal formed Remains of plants, mainly trees, were buried and compressed over millions of years. How carbon dioxide decreased
Describe what happens to the Sun's radiation Short wavelength radiation from the Sun passes through the atmosphere and is absorbed by the Earth's surface, warming it. Greenhouse gases
Explain how deforestation increases carbon dioxide Burning the trees releases carbon dioxide, and fewer trees are left to remove it by photosynthesis. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Describe four different potential effects Give four clearly different effects, each with a short consequence, e.g. sea levels rise, causing flooding. Global climate change
Describe actions to reduce emissions Alternative energy, energy conservation, carbon capture and storage, carbon taxes and licences, carbon off-setting and carbon neutrality. The carbon footprint and its reduction
Describe how carbon monoxide and soot form Incomplete combustion in a limited supply of oxygen produces carbon monoxide and carbon particles (soot). Atmospheric pollutants from fuels
Describe how sulfur dioxide forms Sulfur in the fuel reacts with oxygen when the fuel burns. Atmospheric pollutants from fuels
Explain why carbon monoxide is hard to detect It is colourless and odourless, so you cannot see or smell it. Properties and effects of atmospheric pollutants
Define sustainable development Development that meets the needs of current generations without compromising the ability of future generations to meet their own needs. Using the Earth's resources and sustainable development
Give reasons for each treatment step Filter beds remove solid particles; sterilising with chlorine, ozone or ultraviolet light kills microbes. Potable water
Name two methods of desalination Distillation, and processes that use membranes such as reverse osmosis. Potable water
List the stages of sewage treatment in order Screening and grit removal, sedimentation, anaerobic digestion of the sludge, and aerobic biological treatment of the effluent. Waste water treatment
Explain why new extraction methods are needed Metal ores are limited and copper ores are becoming scarce, so low-grade ores must be used. Alternative methods of extracting metals (HT only)
Describe how phytomining works Plants absorb metal compounds; they are harvested and burned, and the ash contains the metal compounds. Alternative methods of extracting metals (HT only)
Compare plastic and paper bags using an LCA Plastic bags come from crude oil (finite) but can be reused many times; paper bags come from trees but are reused less. Life cycle assessment
Describe how glass and metals are recycled Glass is crushed and melted to make different glass products; metals are melted and recast or reformed. Ways of reducing the use of resources
Explain why recycling saves resources and energy Less of a limited raw material is used, and usually less energy than extracting and processing new material. Ways of reducing the use of resources
Describe energy changes in common situations Say which store decreases and which increases, e.g. a braking car: kinetic store down, thermal store of the brakes up. Energy stores and systems
Calculate kinetic energy Square the speed first, then multiply by the mass and by 0.5. Changes in energy
Calculate elastic potential energy of a spring Use E_e = ½ k e² with the extension in metres, as long as the limit of proportionality is not exceeded. Changes in energy
Calculate energy using ΔE = m c Δθ Find the temperature change first, then multiply mass × specific heat capacity × temperature change. Energy changes in systems
Compare the power of two machines If two motors do the same work, the one that takes less time has the greater power. Power
Explain how lubrication reduces wasted energy Oil reduces friction between moving parts, so less energy is dissipated by heating. Energy transfers in a system
Explain how insulation reduces energy transfer Thermal insulation lowers the rate of energy transfer by heating, e.g. loft insulation in a house. Energy transfers in a system
Give efficiency as a decimal or percentage Multiply the decimal by 100 to get a percentage; efficiency is never more than 1 (100%). Efficiency
Calculate efficiency from power values Divide the useful power output by the total power input. Efficiency
Explain why some resources are more reliable Wind, solar and waves depend on the weather (and solar on the time of day); fossil fuels and nuclear do not. National and global energy resources
Recognise thermistor and LDR symbols Both start from the resistor box: the thermistor has a line with a flat tail through it, the LDR has two arrows pointing in. Standard circuit diagram symbols
Place ammeters and voltmeters correctly Draw an ammeter in series with a component and a voltmeter in parallel across it. Standard circuit diagram symbols
State that current is the same around a loop In a single closed loop the current has the same value at every point. Electrical charge and current
Rearrange V = I R for I or R Use I = V ÷ R and R = V ÷ I, converting kΩ and mA first. Current, resistance and potential difference
Identify an ohmic conductor from its graph At constant temperature, current is directly proportional to pd, so the I–V graph is a straight line through the origin. Resistors
Describe how a diode controls current Current flows in one direction only; the diode has a very high resistance in the reverse direction. Resistors
Find a missing current or pd e.g. the supply pd equals the sum of the pds in series; the total current equals the sum of the branch currents. Series and parallel circuits
Explain the difference between dc and ac A direct pd acts in one direction only; an alternating pd keeps reversing direction. Direct and alternating potential difference
State the potential of each wire Live is about 230 V (compared with earth); neutral is at or close to 0 V; earth is at 0 V. Mains electricity
Rearrange P = V I Use I = P ÷ V, e.g. to find the current an appliance takes from the mains. Power
Calculate energy using E = Q V Charge in coulombs × pd in volts gives energy in joules. Energy transfers in everyday appliances
Rearrange the density equation Use m = ρ × V to find a mass and V = m ÷ ρ to find a volume. Density of materials
Describe the density required practical Measure mass on a balance and find volume from measured dimensions or by displacement of water. Density of materials
Describe particle changes during melting and boiling Describe how the arrangement, spacing and motion of the particles change. Changes of state
Explain why a change of state is physical No new substance is made: if the change is reversed, the material recovers its original properties. Changes of state
State the two possible effects of heating Heating either raises the temperature of the system or produces a change of state. Internal energy
Link temperature to the particles' kinetic energy A higher temperature means the particles have a higher average kinetic energy: they move or vibrate faster. Internal energy
Work out the temperature change Δθ Δθ is the difference between the final and starting temperatures, not the final temperature. Temperature changes in a system and specific heat capacity
Define specific latent heat The amount of energy needed to change the state of 1 kg of a substance with no change in temperature. Changes of state and specific latent heat
Use E = m L Calculate the energy for a change of state with E in J, m in kg and L in J/kg. Changes of state and specific latent heat
Find changes of state on heating graphs Flat sections show a change of state at the melting or boiling point; sloping sections show a temperature change. Changes of state and specific latent heat
Explain how a gas exerts pressure Molecules collide with the walls of the container and exert a force on them; the force on each unit area is the pressure. Particle motion in gases
Compare the sizes of atom and nucleus The nucleus has a radius less than 1/10 000 of the atom's radius, yet contains almost all of its mass. The structure of an atom
Work out protons, neutrons and electrons Protons = atomic number; neutrons = mass number − atomic number; electrons = protons in a neutral atom. Mass number, atomic number and isotopes
Describe the nuclear model A tiny, positively charged nucleus containing most of the mass, with electrons around it. The development of the model of the atom
Compare plum pudding and nuclear models Charge and mass spread out, compared with concentrated in a nucleus with empty space around it. The development of the model of the atom
Describe what each radiation is Alpha: 2 protons and 2 neutrons; beta: a fast electron from the nucleus; gamma: electromagnetic radiation. Radioactive decay and nuclear radiation
State how alpha decay changes a nucleus The mass number falls by 4 and the atomic number falls by 2. Nuclear equations
State how beta decay changes a nucleus The mass number stays the same and the atomic number goes up by 1. Nuclear equations
Explain why gamma emission changes neither number Gamma is electromagnetic radiation with no mass and no charge. Nuclear equations
Explain what random decay means You cannot predict which nucleus will decay or when, but a large sample decays in a predictable way. Half-lives and the random nature of radioactive decay
Find a half-life from a graph Read the time for the activity or count rate to fall to half of any starting value. Half-lives and the random nature of radioactive decay
State that irradiation does not cause radioactivity An irradiated object does not become radioactive. Radioactive contamination
Represent a vector with an arrow The length of the arrow shows the magnitude and the way it points shows the direction. Scalar and vector quantities
Identify the forces acting in a situation For example, a book on a table has its weight acting down and a normal contact force acting up. Contact and non-contact forces
Show forces as vector arrows Draw each arrow from the object, in the direction of the force, with its length showing the size. Contact and non-contact forces
Find mass or g from a weight m = W ÷ g and g = W ÷ m. Gravity
Describe how to measure weight Hang the object from a calibrated spring-balance (a newtonmeter). Gravity
Recognise balanced forces (zero resultant) If the resultant force is zero, the object stays at rest or keeps moving at a steady velocity. Resultant forces
Find force or distance from work done F = W ÷ s and s = W ÷ F. Work done and energy transfer
Convert between joules and newton-metres 1 J = 1 N m, so 250 N m of work is 250 J. Work done and energy transfer
Calculate force or extension with F = ke For example, k = 40 N/m and e = 0.15 m give F = 6.0 N. Forces and elasticity
Describe the spring extension required practical Hang known weights on a spring, measure its length each time, calculate the extension and plot force against extension. Forces and elasticity
Calculate distance and displacement along a line 40 m east then 15 m west: distance 55 m, displacement 25 m east. Distance and displacement
Explain why displacement can be zero After a round trip back to the start, the displacement is zero although the distance travelled is not. Distance and displacement
Find speed or time using s = vt v = s ÷ t and t = s ÷ v. Speed
Calculate average speed for a whole journey Average speed = total distance ÷ total time. Speed
Use + and − signs for velocity Along a line, e.g. +4 m/s to the right and −4 m/s to the left. Velocity
Calculate speed from the gradient Speed = change in distance ÷ change in time for a straight section. The distance–time relationship
Find acceleration from a velocity–time graph Acceleration = gradient = change in velocity ÷ time taken. Acceleration
Explain steady motion using balanced forces A zero resultant force means there is no change in speed or direction. Newton's First Law
Find mass or acceleration using F = ma a = F ÷ m and m = F ÷ a. Newton's Second Law
Describe how acceleration depends on force and mass Acceleration is proportional to the resultant force and inversely proportional to the mass. Newton's Second Law
Identify Third Law partner forces If a boy pushes a wall with 150 N, the wall pushes the boy with 150 N in the opposite direction. Newton's Third Law
Calculate thinking distance using s = v t Thinking distance = speed × reaction time. Stopping distance
Calculate thinking distance from reaction time Thinking distance = speed × reaction time. Reaction time
Describe the ruler-drop reaction time test Catch a dropped ruler; the further it falls before you catch it, the longer your reaction time. Reaction time
Explain the effects of worn tyres and brakes Worn tyres grip the road less; worn brakes produce a smaller friction force. Factors affecting braking distance 1
Calculate the work done by a braking force W = F s, where s is the braking distance. Factors affecting braking distance 2
Link braking force to deceleration The greater the braking force, the greater the deceleration (F = m a). Factors affecting braking distance 2
Recall the momentum equation p = m v Momentum (kg m/s) = mass (kg) × velocity (m/s). Momentum is a property of moving objects
Describe how transverse and longitudinal waves differ Compare the direction of the oscillations with the direction of energy transfer: perpendicular for transverse, parallel for longitudinal. Transverse and longitudinal waves
Identify compressions and rarefactions In a longitudinal wave, compressions are where the particles are close together and rarefactions are where they are spread out. Transverse and longitudinal waves
Use T = 1/f Find the period from the frequency, or the frequency from the period, e.g. f = 50 Hz gives T = 1 ÷ 50 = 0.02 s. Properties of waves
State that all EM waves travel equally fast All EM waves travel at the same speed through a vacuum (space) or air: 3.0 × 10⁸ m/s. Types of electromagnetic waves
Give examples of EM waves transferring energy E.g. infrared from a fire warming your skin, or microwaves heating food in an oven. Types of electromagnetic waves
Draw a ray diagram for refraction Draw the normal; a ray that slows down (e.g. air into glass) bends towards the normal. Properties of electromagnetic waves 1
State which surfaces emit and absorb infrared best Matt black surfaces are the best emitters and absorbers of infrared; shiny silver surfaces are the worst. Properties of electromagnetic waves 1
State the effects of X-rays and gamma rays They are ionising radiation and can cause mutation of genes and cancer. Properties of electromagnetic waves 2
State where gamma rays come from Gamma rays come from changes in the nucleus of an atom. Properties of electromagnetic waves 2
Give uses of visible light and ultraviolet Visible light: fibre optic communications. Ultraviolet: energy-efficient lamps and sun tanning. Uses and applications of electromagnetic waves
Describe the difference between permanent and induced magnets A permanent magnet produces its own magnetic field; an induced magnet only becomes a magnet when it is placed in a magnetic field. Poles of a magnet
Plot a magnetic field using a compass Mark where the compass needle points, move the compass on, repeat, then join the dots from N to S. Magnetic fields
State how field strength depends on distance The field is strongest at the poles and gets weaker further from the magnet. Magnetic fields
Draw the field around a straight wire Circles centred on the wire, further apart further out, with arrows showing the direction. Electromagnetism
State what affects the strength of the field The field is stronger for a bigger current, and weaker further from the wire. Electromagnetism
Recall the factors that affect the force The force is bigger for a stronger field (greater magnetic flux density), a bigger current and a longer length of wire in the field. Fleming's left-hand rule (HT only)
Use Fleming's left-hand rule to find direction First finger = field (N to S), second finger = current (+ to −), thumb = force (motion). Fleming's left-hand rule (HT only)
Explain why a current-carrying wire moves The magnetic field of the current interacts with the field of the magnet, producing a force on the wire. Fleming's left-hand rule (HT only)
Explain why the coil's sides feel opposite forces The current is in opposite directions in the two sides, so the forces on them are in opposite directions. Electric motors (HT only)

Grade 6

Grade 6 checklist (PDF)

Write cell sizes in standard form Use 1 µm = 10⁻⁶ m and 1 nm = 10⁻⁹ m, e.g. 4 µm = 4 × 10⁻⁶ m. Eukaryotes and prokaryotes
Link a cell's structures to its function e.g. a cell that needs a lot of energy has many mitochondria for respiration. Animal and plant cells
Explain how each adaptation helps the cell Give the feature and what it does, e.g. the root hair gives a large surface area for absorbing water. Cell specialisation
Explain the importance of cell differentiation It produces the different specialised cells a multicellular organism needs to carry out different functions. Cell differentiation
Convert units in magnification calculations Put the image size and the real size in the same unit, usually µm, before dividing. Microscopy
Explain why body cell chromosomes are paired One chromosome of each pair came from each parent, in the egg and the sperm. Chromosomes
Link genes to proteins A gene is a small section of DNA that codes for a particular protein. Chromosomes
Describe therapeutic cloning and its advantage An embryo is made with the same genes as the patient, so its stem cells are not rejected. Stem cells
Calculate surface area to volume ratios Work out the total surface area and the volume, then write the ratio as x : 1. Diffusion
Explain how exchange surfaces are adapted Large surface area, thin membrane, good blood supply and ventilation, e.g. alveoli and villi. Diffusion
Calculate a rate of change in mass Change in mass ÷ time, e.g. in g per minute. Osmosis
Explain gains and losses in mass Tissue gains mass when the solution is more dilute than the cell contents, and loses mass when it is more concentrated. Osmosis
Explain osmosis in animal and plant cells Animal cells can burst in water or shrivel in concentrated solutions; a plant cell wall stops the cell bursting. Osmosis
Compare diffusion, osmosis and active transport Compare what moves, which way it moves relative to the concentration gradient, and whether energy is needed. Active transport
Explain why root hair cells have many mitochondria More respiration releases more energy for the active transport of mineral ions. Active transport
Explain why a structure is an organ Say that it is made of several different tissues that work together to carry out a specific function. Principles of organisation
Explain enzyme action using lock and key The substrate fits the specifically shaped active site, so each enzyme catalyses only one reaction. The human digestive system
Explain how bile speeds up fat digestion Bile is alkaline, so it neutralises stomach acid, and it emulsifies fat into small droplets with a larger surface area for lipase. The human digestive system
Explain how blood vessels suit their functions Arteries have thick muscular, elastic walls for high pressure, veins have valves, and capillary walls are one cell thick for diffusion. The heart and blood vessels
Calculate the rate of blood flow Rate of blood flow = volume of blood ÷ time, e.g. in cm³ per minute. The heart and blood vessels
Explain how red blood cells are adapted A biconcave shape gives a large surface area, and having no nucleus leaves more room for haemoglobin, which carries oxygen. Blood
Describe how white blood cells defend the body They engulf pathogens (phagocytosis), produce antibodies and produce antitoxins. Blood
Explain how CHD damages the heart muscle Less blood flows through the narrowed coronary arteries, so the heart muscle gets less oxygen for respiration. Coronary heart disease: a non-communicable disease
Explain the consequences of a faulty valve A valve that does not open fully or that leaks makes the heart pump blood less efficiently, so less oxygen reaches the body. Coronary heart disease: a non-communicable disease
Describe how different diseases can interact Immune defects increase infections, viruses can trigger cancers, immune reactions can trigger allergies, and severe physical illness can lead to depression. Health issues
Calculate and interpret values from disease data Read values from tables and graphs, calculate rates per 1000 people or percentages, and describe trends. Health issues
Describe a correlation shown in a scatter diagram Say whether the correlation is positive or negative and quote data from the graph. The effect of lifestyle on some non-communicable diseases
Discuss human and financial costs of disease Consider suffering and early death as well as treatment costs and lost work, for individuals, communities, nations and the world. The effect of lifestyle on some non-communicable diseases
Explain how a secondary tumour forms Cells break off a malignant tumour, travel in the blood to another part of the body and divide there to form a new tumour. Cancer
Explain genetic risk factors for cancer Some people inherit alleles, such as faulty BRCA alleles, that increase their risk of certain cancers. Cancer
Explain how the mesophyll layers are adapted Palisade cells are packed with chloroplasts near the top of the leaf; spongy mesophyll has air spaces for gases to diffuse through. Plant tissues
Describe what guard cells and stomata do Guard cells open and close the stomata to control gas exchange and water loss. Plant tissues
Explain factors affecting the rate of transpiration Higher temperature, lower humidity, more air movement and higher light intensity all increase the rate. Plant organ system
Calculate the rate of transpiration Rate = volume (or mass) of water lost or taken up ÷ time, e.g. from a potometer. Plant organ system
Explain how a control method stops spread Link the method to the route, e.g. washing hands removes pathogens, so they are not passed on by direct contact. Communicable (infectious) diseases
Explain why TMV reduces plant growth The discoloured parts of the leaves have less chlorophyll, so there is less photosynthesis and less glucose for growth. Viral diseases
Explain why gonorrhoea is harder to treat now Many strains are resistant to penicillin, so penicillin no longer kills them and other antibiotics must be used. Bacterial diseases
Explain how vaccinating poultry protects people Vaccinated chickens are not infected, so their meat and eggs are less likely to carry the bacteria. Bacterial diseases
Explain why black spot reduces growth Spotted, yellow and fallen leaves mean less photosynthesis, so less glucose is made for growth. Fungal diseases
Explain how each control method reduces spread Fewer mosquitoes, or fewer bites, means the protist is passed to fewer people. Protist diseases
Explain how antibodies and antitoxins work Antibodies bind to specific antigens on pathogens; antitoxins bind to the toxins made by bacteria and neutralise them. Human defence systems
Explain how vaccination reduces spread in populations If most people are immune, the pathogen is unlikely to reach unvaccinated people, so it spreads much less. Vaccination
Explain why antiviral drugs are hard to develop Viruses reproduce inside body cells, so drugs that kill them are likely to damage body tissues too. Antibiotics and painkillers
Explain why a placebo is used A placebo contains no drug, so comparing the two groups shows whether the drug itself has an effect. Discovery and development of drugs
Explain why results are peer reviewed Other experts check the method, results and conclusions before publication, so false or biased claims are less likely to be published. Discovery and development of drugs
Explain the results of a leaf starch test Only parts of a leaf that had light and chlorophyll made glucose, which was stored as starch and turns iodine solution blue-black. Photosynthetic reaction
Explain why plants store starch, not glucose Starch is insoluble, so it does not affect the movement of water by osmosis and it stays inside the cells. Uses of glucose from photosynthesis
Explain why plants need nitrate ions Plants use glucose and nitrate ions to make amino acids, which are joined to make proteins. Uses of glucose from photosynthesis
Compare aerobic and anaerobic respiration Compare the need for oxygen, the products and the amount of energy transferred. Aerobic and anaerobic respiration
Explain muscle fatigue in long exercise Lactic acid builds up from anaerobic respiration, and over long vigorous exercise muscles stop contracting efficiently. Response to exercise
Explain why metabolism needs respiration and enzymes Building new molecules uses energy transferred by respiration, and each reaction is controlled by enzymes. Metabolism
Describe what happens to excess protein Excess proteins are broken down to form urea, which is excreted. Metabolism
Apply the control system to new contexts Pick out the stimulus, receptor, coordination centre, effector and response in an unfamiliar example. Homeostasis
Explain how impulses cross a synapse A chemical is released, diffuses across the gap and binds to receptors on the next neurone, starting a new impulse. The human nervous system
Explain how neurones are adapted Long axons carry impulses a long way, branched endings connect to many neurones, and a fatty sheath speeds impulses up. The human nervous system
Explain why the pituitary is the 'master gland' Its hormones act on other glands, stimulating them to release their own hormones. Human endocrine system
Interpret blood glucose graphs Describe and explain the rise and fall of glucose after a meal, with and without diabetes. Control of blood glucose concentration
Interpret hormone graphs of the menstrual cycle Match each hormone's peak to events such as ovulation and the build-up of the uterus lining. Hormones in human reproduction
Evaluate different methods of contraception Compare effectiveness, side effects, STI protection, convenience and whether the method is reversible. Contraception
Describe the main stages of IVF Give FSH and LH, collect eggs, fertilise them in the lab, then insert one or two embryos. The use of hormones to treat infertility (HT only)
Define negative feedback A change away from normal triggers a response that reverses the change, returning the level to normal. Feedback systems (HT only)
Explain why sexually produced offspring vary Genetic information from two parents is mixed, so each offspring gets a different combination of alleles. Sexual and asexual reproduction
Explain why asexual offspring are clones There is no fusion of gametes and no mixing of genetic information, and only mitosis is involved. Sexual and asexual reproduction
Explain why gametes have half the chromosomes So that fertilisation restores the normal number of chromosomes. Meiosis
Describe development after fertilisation The new cell divides by mitosis, the number of cells increases and the cells differentiate as the embryo develops. Meiosis
Explain how a gene makes a protein Each gene codes for a particular sequence of amino acids, which makes a specific protein. DNA and the genome
Give three uses of the human genome Finding genes linked to disease, understanding and treating inherited disorders, and tracing past human migration. DNA and the genome
Extract information from family trees Use the key and the phenotypes of parents and children to work out genotypes. Genetic inheritance
Predict disorder risks using Punnett squares For example, two carriers of cystic fibrosis have a 0.25 probability of an affected child. Inherited disorders
Explain the 0.5 chance of a boy All eggs carry an X chromosome and half of sperm carry X, half carry Y. Sex determination
Describe how mutations affect phenotype All variants arise from mutations: most have no effect on the phenotype, some influence it and very few determine it. Variation
Explain how a feature evolved Link variation to survival and reproduction, and the allele becoming more common over many generations. Evolution
Explain when populations become separate species When they can no longer interbreed to produce fertile offspring. Evolution
Explain the problems caused by inbreeding Breeds become prone to disease or inherited defects because variation is reduced. Selective breeding
Give benefits and concerns of GM crops Higher yields, against concerns about wild flowers, insects and effects on human health. Genetic engineering
Explain how fossils support evolution Fossils from rocks of different ages show how organisms have changed over millions of years. Evidence for evolution
Explain why the fossil record is incomplete Early soft-bodied organisms left few traces, and most traces were destroyed by geological activity. Fossils
Explain uncertainty about how life began So few traces of early life remain that scientists cannot be certain how life began. Fossils
Explain how a factor leads to extinction Link the factor to fewer individuals surviving and reproducing until none are left. Extinction
Explain how resistant strains develop A mutation makes some bacteria resistant; they survive the antibiotic and reproduce, so the resistant population rises. Resistant bacteria
Explain why the three-domain system was introduced Evidence from chemical analysis showed that some organisms are more different than their structure suggests. Classification of living organisms
Define a stable community All the species and environmental factors are in balance, so population sizes stay fairly constant. Communities
Explain how an abiotic change affects a species Link the factor to a life process, e.g. less light means less photosynthesis, so slower growth. Abiotic factors
Explain effects of new predators or pathogens Prey may not be adapted to escape a new predator and organisms may have no resistance to a new pathogen, so numbers can fall fast. Biotic factors
Explain adaptations to hot, cold and dry environments Link each feature to heat loss or water loss, e.g. spines instead of leaves reduce water loss. Adaptations
Estimate population size from quadrat data Mean number per m² × total area in m². Levels of organisation
Use a transect to investigate distribution Place quadrats at regular intervals along a line and measure the factor at each point. Levels of organisation
Explain the role of decomposers in cycling Microorganisms break down dead matter and waste, respire and release carbon dioxide, and return mineral ions to the soil. How materials are cycled
Explain why high biodiversity makes ecosystems stable Species depend less on any one other species for food, shelter and maintaining the physical environment. Biodiversity
Explain the effects of acidic gases Gases such as sulfur dioxide dissolve in rain to make acid rain, which damages trees and makes lakes acidic. Waste management
Explain how destroying peat bogs affects biodiversity Less bog habitat means fewer of the plants, animals and microorganisms that live there can survive, so biodiversity falls. Land use
Explain how deforestation increases atmospheric carbon dioxide Burning releases carbon dioxide, microorganisms respire as the wood decays, and fewer trees remove carbon dioxide by photosynthesis. Deforestation
Explain why species distributions change As temperature or rainfall changes, species survive and breed in new areas and die out where conditions no longer suit them. Global warming
Describe positive and negative human interactions For example, replanting hedgerows is positive, while removing them to make bigger fields is negative. Maintaining biodiversity
Balance symbol equations Change only the large numbers in front of formulae until every element has the same number of atoms on each side. Atoms, elements and compounds
Choose a method from given data Use information about solubility and boiling points to choose and justify a separation technique. Mixtures
Compare plum pudding and nuclear models Positive charge and mass spread out, compared with concentrated in a tiny nucleus with mostly empty space around it. The development of the model of the atom
Work out a particle's overall charge Charge = protons − electrons, e.g. 12 protons and 10 electrons gives a 2+ ion. Relative electrical charges of subatomic particles
Find protons, neutrons and electrons in ions Protons and neutrons as in the atom; one electron fewer for each + charge, one more for each − charge. Size and mass of atoms
Decide which isotope is more abundant The A_r is closer to the mass number of the more abundant isotope. Relative atomic mass
Give the electronic structure of simple ions Remove or add outer electrons, e.g. Na⁺ is 2,8 and Cl⁻ is 2,8,8. Electronic structure
Explain why it is called 'periodic' Similar properties occur at regular intervals as the atomic number increases. The periodic table
Explain why Mendeleev's table was accepted Elements were later discovered that filled the gaps and had the properties he predicted. Development of the periodic table
Classify an element using data Use melting point, conductivity, appearance and the type of oxide as evidence. Metals and non-metals
Predict a property from a trend Estimate a missing value in a table so that it fits the pattern. Group 0
Explain why helium is also unreactive Its only shell is the first shell, which is full with 2 electrons. Group 0
Explain their similar reactions using electrons They all have one electron in their outer shell, which they lose to form 1+ ions. Group 1
Predict properties of rubidium and caesium Use the trends: even more vigorous reactions and similar products, e.g. RbOH and RbCl. Group 1
Write equations for displacement reactions e.g. Cl₂ + 2NaBr → 2NaCl + Br₂, with the colour change. Group 7
Describe what the electrons do in each bond Electrons are transferred (ionic), shared in pairs (covalent) or delocalised (metallic). Chemical bonds
Work out the formula of an ionic compound Balance the charges so the total is zero, e.g. Ca²⁺ and Cl⁻ give CaCl₂. Ionic bonding
Work out an empirical formula from a diagram Count the ions of each type and simplify the ratio, e.g. 8 : 16 gives XY₂. Ionic compounds
Draw molecules with double and triple bonds Oxygen, O₂, has a double bond (two shared pairs); nitrogen, N₂, has a triple bond (three shared pairs). Covalent bonding
Deduce a molecular formula from a diagram Count every atom of each element in one molecule, e.g. C₂H₆ for ethane. Covalent bonding
Explain why the metal particles are positive ions Each atom has lost its outer electrons to the delocalised electrons, so it has more protons than electrons. Metallic bonding
Link melting and boiling points to forces The stronger the forces between the particles, the more energy is needed and the higher the melting and boiling points. The three states of matter
Recognise that single atoms lack bulk properties One atom does not have properties such as colour, melting point or conductivity; these come from huge numbers of particles. The three states of matter
Tell (l) apart from (aq) Water itself and molten substances are (l); substances dissolved in water are (aq). State symbols
Explain conduction in terms of moving ions When molten or dissolved, the ions are free to move and carry charge; in the solid they are held in fixed positions. Properties of ionic compounds
Say which forces are overcome on boiling The intermolecular forces are overcome; the covalent bonds inside the molecules do not break. Properties of small molecules
Explain why polymers are solids at room temperature Their large molecules have relatively strong intermolecular forces, which need more energy to overcome than those between small molecules. Polymers
Recognise giant covalent structures from diagrams A network of atoms all joined by covalent bonds, continuing in all directions, with no separate molecules. Giant covalent structures
Explain why alloys are harder than pure metals Atoms of different sizes distort the layers, so the layers cannot slide over each other as easily. Properties of metals and alloys
Explain thermal conduction in metals Energy is transferred through the metal by the delocalised electrons. Metals as conductors
Explain why diamond does not conduct electricity All four outer electrons of each carbon atom are used in bonds, so there are no delocalised electrons. Diamond
Explain why graphite conducts electricity One electron from each carbon atom is delocalised and can move through the structure, carrying charge. Graphite
Explain graphite's very high melting point The many strong covalent bonds within the layers must be broken. Graphite
Explain the properties of graphene Strong covalent bonds make it very strong; delocalised electrons let it conduct electricity. Graphene and fullerenes
Write balanced equations from word equations Write the correct formula for each substance (e.g. O₂, H₂, HCl, MgCl₂) and then balance it. Conservation of mass and balanced chemical equations
Calculate percentage by mass of an element Divide the total A_r of that element in the formula by the M_r, then multiply by 100. Relative formula mass
Use an equation to predict the mass change Look for (g): a gas reactant means the mass goes up, a gas product means it goes down. Mass changes when a reactant or product is a gas
Calculate the uncertainty from the range Uncertainty = ± half the range, e.g. a range of 0.4 g gives ± 0.2 g. Chemical measurements
Calculate moles from mass moles = mass (g) ÷ M_r. Moles (HT only)
Calculate the masses shown in an equation For each substance, mass = balancing number × M_r, e.g. 2H₂O is 36 g. Amounts of substances in equations (HT only)
Convert each reacting mass into moles Divide each mass by its M_r, using O₂, H₂, Cl₂ or N₂ for gaseous elements. Using moles to balance equations (HT only)
Explain why a reactant is used in excess To make sure that all of the other reactant is used up. Limiting reactants (HT only)
Predict how the limiting reactant affects product The amount of product is proportional to the amount of limiting reactant; extra excess reactant makes no more product. Limiting reactants (HT only)
Calculate the mass of solute in a solution Mass = concentration (g/dm³) × volume (dm³). Concentration of solutions
Balance equations for metals reacting with oxygen Write correct formulae first, then balance with numbers in front, e.g. 4Na + O₂ → 2Na₂O. Metal oxides
Write equations for displacement reactions For example, zinc + copper sulfate → zinc sulfate + copper. The reactivity series
Identify what is oxidised and reduced The metal oxide loses oxygen so it is reduced; carbon gains oxygen so it is oxidised. Extraction of metals and reduction
Identify the species oxidised and reduced An atom that becomes a positive ion is oxidised; a positive ion that becomes an atom is reduced. Oxidation and reduction in terms of electrons (HT only)
Write balanced symbol equations for these reactions For example, Zn + H₂SO₄ → ZnSO₄ + H₂. Reactions of acids with metals
Work out salt formulae from ion charges Balance the charges so they add to zero, e.g. Ca²⁺ and NO₃⁻ give Ca(NO₃)₂. Neutralisation of acids and salt production
Describe the full method for a salt Warm acid, add solid until in excess, filter, evaporate some water, crystallise, then dry the crystals. Soluble salts
Write the ionic equation for neutralisation H⁺(aq) + OH⁻(aq) → H₂O(l). The pH scale and neutralisation
Define strong and weak acids A strong acid is completely ionised in aqueous solution; a weak acid is only partially ionised. Strong and weak acids (HT only)
Explain the terms dilute and concentrated They describe the amount of acid in a given volume of solution, not how much it ionises. Strong and weak acids (HT only)
Explain why solid ionic compounds do not conduct In a solid the ions are held in fixed positions in a lattice, so they cannot move to carry charge. The process of electrolysis
Explain how each product forms Metal ions are attracted to the cathode and gain electrons; non-metal ions are attracted to the anode and lose electrons. Electrolysis of molten ionic compounds
Explain why cryolite is used Mixing aluminium oxide with cryolite lowers the melting point, so less energy is needed. Using electrolysis to extract metals
Explain where hydrogen and hydroxide ions come from A small number of water molecules break down into hydrogen ions and hydroxide ions. Electrolysis of aqueous solutions
Describe tests for the gases produced Hydrogen gives a squeaky pop, oxygen relights a glowing splint and chlorine bleaches damp litmus paper. Electrolysis of aqueous solutions
Write cathode half equations for metal ions For example, Cu²⁺ + 2e⁻ → Cu. Representation of reactions at electrodes as half equations (HT only)
Write anode half equations for halide ions For example, 2Cl⁻ → Cl₂ + 2e⁻. Representation of reactions at electrodes as half equations (HT only)
Describe the temperature change required practical Mix measured amounts in a polystyrene cup, stir, and record the starting and the highest (or lowest) temperature. Energy transfer during exothermic and endothermic reactions
Evaluate uses of exothermic and endothermic reactions Judge hand warmers, self-heating cans and cold packs using given data on temperature change, cost, safety and reuse. Energy transfer during exothermic and endothermic reactions
Draw a reaction profile Show the reactants and products at the correct relative heights, a curve with a peak above both, and labelled arrows. Reaction profiles
Count the bonds in displayed formulae Find how many of each type of bond there are, e.g. H–O–H has two O–H bonds and O=C=O has two C=O bonds. The energy change of reactions (HT only)
Explain exothermic or endothermic using bond energies Compare the energy needed to break the bonds with the energy released when the new bonds form. The energy change of reactions (HT only)
Draw a tangent to a rate curve Draw a straight line that touches the curve at the chosen time; its slope is a measure of the rate at that time. Calculating rates of reactions
Sketch rate curves for changed conditions A faster reaction has a steeper start and levels off sooner, at the same height if the amounts of reactants are the same. Factors which affect the rates of chemical reactions
Identify and control the variables Independent: concentration; dependent: time taken or volume of gas; control: temperature, volumes, and mass and size of solid. Factors which affect the rates of chemical reactions
Explain the effect of temperature fully Particles move faster, so collisions are more frequent and more energetic, and more of them have at least the activation energy. Collision theory and activation energy
Explain how a catalyst increases the rate It provides a different pathway for the reaction that has a lower activation energy. Catalysts
Draw a reaction profile with a catalyst Show a lower peak between the same reactant and product energy levels. Catalysts
Explain how conditions change the direction Changing a condition such as temperature can make the forward or the reverse reaction happen. Reversible reactions
Use observations as evidence of reversibility E.g. a white solid re-forming at the cool top of a heated tube shows the reverse reaction happening. Reversible reactions
Link the colour changes to energy changes Blue to white takes in energy (endothermic); white to blue gives out energy (exothermic). Energy changes and reversible reactions
Give the energy change for the reverse reaction Same amount, opposite direction: e.g. forward takes in 50 kJ, reverse gives out 50 kJ. Energy changes and reversible reactions
Explain why the equilibrium is dynamic Both the forward and reverse reactions are still happening, at the same rate. Equilibrium
Find when equilibrium is reached from data Equilibrium starts when the amounts or concentrations stop changing (the lines become horizontal). Equilibrium
Explain what shifting right or left means Shifting right gives more products at equilibrium; shifting left gives more reactants. The effect of changing conditions on equilibrium (HT only)
Know a catalyst does not move equilibrium A catalyst speeds up both reactions equally, so equilibrium is reached faster but its position does not change. The effect of changing conditions on equilibrium (HT only)
Predict the effect of removing a product More reactants react until equilibrium is reached again, so more product forms. The effect of changing concentration (HT only)
Predict the effect of adding more product The position shifts to the left, so more reactants form. The effect of changing concentration (HT only)
Predict heating an endothermic reaction Raising the temperature increases the relative amount of products at equilibrium. The effect of temperature changes on equilibrium (HT only)
Predict the effect of increasing the pressure The position shifts towards the side with the smaller number of molecules. The effect of pressure changes on equilibrium (HT only)
Predict the effect of decreasing the pressure The position shifts towards the side with the larger number of molecules. The effect of pressure changes on equilibrium (HT only)
Describe the features of a homologous series Same general formula, each member differs from the next by CH₂, similar chemical reactions and a gradual trend in physical properties. Crude oil, hydrocarbons and alkanes
Explain fractional distillation using evaporation and condensation Crude oil is evaporated; the vapours rise and each hydrocarbon condenses where the temperature falls below its boiling point. Fractional distillation and petrochemicals
Balance complete combustion equations Balance C, then H, then O; if you need half an O₂, double every number. Properties of hydrocarbons
Balance cracking equations The total numbers of carbon and hydrogen atoms must be the same on both sides, e.g. C₁₀H₂₂ → C₈H₁₈ + C₂H₄. Cracking and alkenes
Explain why cracking is needed using data The supply of long-chain fractions is greater than demand, and the demand for short-chain fuels is greater than supply. Cracking and alkenes
Calculate masses and percentages in formulations Mass of component = percentage ÷ 100 × total mass, and the reverse. Formulations
Name the stationary and mobile phases The paper is the stationary phase; the solvent is the mobile phase that moves through it. Chromatography
Give Rf values to suitable significant figures Rf has no units; give it to the significant figures asked for, usually 2. Chromatography
Explain the pop with an equation Hydrogen reacts rapidly with oxygen in the air: 2H₂ + O₂ → 2H₂O. Test for hydrogen
Explain why the splint relights The gas has a much higher concentration of oxygen than air (about 20%), so the splint burns fast enough to relight. Test for oxygen
Identify gases using all four tests Match each result to hydrogen, oxygen, carbon dioxide or chlorine. Test for chlorine
Use ratios and fractions for gases in air Nitrogen : oxygen is about 80 : 20, which simplifies to 4 : 1, and four-fifths is the same as 80%. The proportions of different gases in the atmosphere
Explain how the oceans removed carbon dioxide Carbon dioxide dissolved in the oceans and carbonates were precipitated, forming sediments. The Earth's early atmosphere
Explain why evidence about it is limited The time scale is about 4.6 billion years, so no one could measure it and little evidence survives. The Earth's early atmosphere
Describe how the percentage of oxygen increased Over the next billion years plants evolved and oxygen gradually increased to a level that let animals evolve. How oxygen increased
Explain two effects of photosynthesis on air Photosynthesis adds oxygen to the atmosphere and removes carbon dioxide from it at the same time. How oxygen increased
Describe how crude oil and natural gas formed Remains of plankton buried in mud on the sea bed were changed by heat and pressure over millions of years. How carbon dioxide decreased
Describe the greenhouse effect using wavelengths The warm surface emits long wavelength radiation, which greenhouse gases absorb and re-emit in all directions. Greenhouse gases
Explain why peer review matters Other experts check the methods, data and conclusions before publication, which reduces errors and bias. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Describe trends in carbon dioxide data Quote values from a graph or table and calculate changes, e.g. the increase or percentage increase over a period. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Explain how warming causes sea levels to rise Ice on land melts and flows into the sea, and sea water expands as it warms. Global climate change
Give reasons why actions may be limited Scientific disagreement, lack of public information and education, lifestyle changes, economic considerations and incomplete international cooperation. The carbon footprint and its reduction
Describe actions to reduce methane emissions For example, collect methane from landfill to use as a fuel, send less waste to landfill, and reduce livestock numbers. The carbon footprint and its reduction
Describe how oxides of nitrogen form At the high temperatures in engines, nitrogen and oxygen from the air react together. Atmospheric pollutants from fuels
Explain how particulates cause global dimming Particulates reflect sunlight back into space, so less sunlight reaches the Earth's surface. Properties and effects of atmospheric pollutants
Describe the health effects of these pollutants Sulfur dioxide and oxides of nitrogen cause respiratory problems, and particulates can damage the lungs. Properties and effects of atmospheric pollutants
Classify a resource as finite or renewable Use the information given: compare how quickly the resource forms or regrows with how quickly it is used. Using the Earth's resources and sustainable development
Describe the water purification required practical Test the pH, find the mass of dissolved solids by evaporation, and purify the water by distillation. Potable water
Describe what happens at each stage For example, in sedimentation solids settle to form sludge, leaving the liquid effluent on top. Waste water treatment
State what industrial waste water needs Removal of organic matter and harmful chemicals. Waste water treatment
Describe how bioleaching works Bacteria are used to produce leachate solutions that contain metal compounds. Alternative methods of extracting metals (HT only)
Name ways to get copper from solutions Displacement using scrap iron, or electrolysis. Alternative methods of extracting metals (HT only)
Calculate totals from LCA data tables Add up the values for each stage, and compare products per item or per use. Life cycle assessment
Explain why separation is needed for recycling The amount of separation depends on the material and the properties required of the final product. Ways of reducing the use of resources
Include wasted energy in your descriptions Say that friction or air resistance dissipates some energy to the thermal store of the surroundings. Energy stores and systems
Convert units before you substitute Change grams to kilograms, centimetres to metres and kilojoules to joules first. Changes in energy
Rearrange to find c, m or Δθ E.g. c = ΔE ÷ (m × Δθ) or Δθ = ΔE ÷ (m × c). Energy changes in systems
Describe the specific heat capacity practical Heat a metal block of known mass with an electric heater, measuring the energy supplied and the temperature rise. Energy changes in systems
Convert kW, kJ and minutes first Change kilowatts to watts, kilojoules to joules and minutes to seconds before you substitute. Power
Rearrange to find energy or time E = P × t and t = E ÷ P. Power
Link thermal conductivity to rate of transfer The higher the thermal conductivity, the higher the rate of energy transfer by conduction through a material. Energy transfers in a system
Describe how walls affect a building's cooling Thicker walls made of a material with a lower thermal conductivity make a building cool more slowly. Energy transfers in a system
Find the wasted or useful energy Wasted energy = total input − useful output, so useful output = total input − wasted energy. Efficiency
Describe the environmental impact of each resource E.g. burning fossil fuels releases carbon dioxide; hydro-electric dams flood valleys. National and global energy resources
Interpret circuit diagrams with junctions Work out which components are in series and which are on parallel branches. Standard circuit diagram symbols
Rearrange Q = I t and convert units Use I = Q ÷ t or t = Q ÷ I, converting minutes to seconds and mA to A first. Electrical charge and current
Describe the resistance of a wire practical Measure V and I for different lengths of wire and calculate R = V ÷ I each time. Current, resistance and potential difference
Explain the filament lamp I–V graph The line curves because the filament gets hotter as the current increases, so its resistance increases. Resistors
Describe the I–V characteristics practical Vary the pd with a variable resistor, record V and I, then reverse the connections for negative values. Resistors
Explain how added resistors change total resistance Series increases the total resistance; parallel decreases it. Series and parallel circuits
Interpret pd–time graphs for ac and dc A steady dc supply is a horizontal line; ac is a wave that goes positive and negative. Direct and alternating potential difference
Explain how the earth wire keeps you safe It stops the appliance becoming live and only carries a current if there is a fault. Mains electricity
Calculate power using P = I² R Square the current first, then multiply by the resistance. Power
Relate power ratings to energy transferred An appliance with a higher power rating transfers more energy each second. Energy transfers in everyday appliances
Explain why a high pd means low current For the same power, P = V I, so increasing the pd decreases the current. The National Grid
Explain density differences between states using particles Gas particles are far apart, so each cubic metre of gas contains much less mass than a cubic metre of solid or liquid. Density of materials
Convert between g/cm³ and kg/m³ 1 g/cm³ = 1000 kg/m³, because 1 kg = 1000 g and 1 m³ = 1 000 000 cm³. Density of materials
Explain why density changes but mass does not The particles move closer together or further apart, so the volume changes but the number of particles does not. Changes of state
Explain mass changes in an open container Particles can escape into the air, so the container's mass drops even though the total mass is conserved. Changes of state
Explain how temperature differs from internal energy A large mass at a low temperature can have more internal energy than a small mass at a high temperature, because it has many more particles. Internal energy
Rearrange to find c, m or Δθ Use c = ΔE ÷ (m Δθ), m = ΔE ÷ (c Δθ) or Δθ = ΔE ÷ (m c). Temperature changes in a system and specific heat capacity
Explain what affects a temperature rise The rise depends on the mass heated, the material (its specific heat capacity) and the energy supplied. Temperature changes in a system and specific heat capacity
Distinguish latent heat of fusion and vaporisation Fusion: changing between solid and liquid. Vaporisation: changing between liquid and vapour (gas). Changes of state and specific latent heat
Tell specific heat capacity from specific latent heat Specific heat capacity is for a temperature change with no change of state; specific latent heat is for a change of state with no temperature change. Changes of state and specific latent heat
Explain pressure rise when heated at constant volume Faster molecules collide with the walls more often and with more force, so the pressure increases. Particle motion in gases
Explain how electrons change energy level Absorbing EM radiation moves an electron to a higher level, further out; emitting EM radiation moves it to a lower level, closer in. The structure of an atom
Compare sizes using standard form Divide the larger size by the smaller one, e.g. 1 × 10⁻¹⁰ m ÷ 1 × 10⁻¹⁴ m = 10 000. The structure of an atom
Define and identify isotopes Isotopes are atoms with the same number of protons but different numbers of neutrons. Mass number, atomic number and isotopes
Explain how an atom becomes a positive ion Losing one or more outer electrons leaves more protons than electrons, so the particle is positive. Mass number, atomic number and isotopes
Explain each alpha scattering observation Link 'straight through', 'deflected' and 'bounced back' to what each shows about the atom. The development of the model of the atom
Explain how a beta particle is formed A neutron in the nucleus turns into a proton, and a high-speed electron is ejected. Radioactive decay and nuclear radiation
Compare penetration, range and ionising power Alpha is the most ionising with the shortest range; gamma is the least ionising with the longest range. Radioactive decay and nuclear radiation
Complete a nuclear equation Make the mass numbers and the atomic numbers balance on both sides of the arrow. Nuclear equations
Calculate activity after whole half-lives Halve the activity once for each half-life that passes. Half-lives and the random nature of radioactive decay
Find a half-life from data Count the number of halvings in the time given, then divide the time by that number. Half-lives and the random nature of radioactive decay
Explain why findings are peer reviewed Published findings can be checked by other scientists, so the conclusions are more reliable. Radioactive contamination
Compare the hazards of contamination and irradiation Contamination keeps exposing you until it is removed or decays; irradiation stops when the source is removed. Radioactive contamination
Draw and read vector arrows to scale With a scale of 1 cm = 5 N, a 4.0 cm arrow represents a 20 N force. Scalar and vector quantities
Describe the forces between interacting objects Each object exerts a force on the other; the two forces are equal in size and opposite in direction. Contact and non-contact forces
Explain why weight changes but mass does not Weight depends on the gravitational field strength where the object is; mass is the amount of matter and stays the same. Gravity
State where the weight of an object acts The weight of an object can be treated as acting at a single point called its centre of mass. Gravity
Draw and use free body diagrams Show every force acting on one object as a labelled arrow drawn from the object. Resultant forces
Explain heating by work done against friction Work done against friction transfers energy to the thermal store, so the temperature of the object rises. Work done and energy transfer
Interpret linear and non-linear force–extension graphs A straight line through the origin shows F ∝ e with gradient k; the line curves beyond the limit of proportionality. Forces and elasticity
Give displacement as magnitude and direction For example 25 m east, 300 m on a bearing of 045°, or −5 m along a line. Distance and displacement
Convert units of distance, time and speed km to m × 1000, minutes to seconds × 60, km/h to m/s ÷ 3.6. Speed
Explain when velocity changes Velocity changes if the speed changes, if the direction changes, or if both change. Velocity
Calculate average speed from a graph Read the total distance and total time, then divide. The distance–time relationship
Use the equation v² − u² = 2as It is on the equations sheet and applies to uniform acceleration; rearrange it for a, s, u or v. Acceleration
Explain terminal velocity for a falling object It accelerates at first; drag increases with speed until the resultant force is zero. Acceleration
Explain changing motion using resultant force Velocity (speed and/or direction) only changes if a resultant force acts. Newton's First Law
Use the resultant force in F = ma Find the resultant first, e.g. thrust minus drag, then divide by the mass. Newton's Second Law
Describe the acceleration required practical Vary the force (or the mass) on a trolley and measure its acceleration, e.g. with light gates. Newton's Second Law
Describe the features of a Third Law pair Same size, opposite directions, same type of force, acting on two different objects. Newton's Third Law
Explain motion using the Third Law A swimmer pushes water backwards; the water pushes the swimmer forwards. Newton's Third Law
Explain how speed affects stopping distance For a given braking force, a greater speed gives a greater thinking distance and a greater braking distance. Stopping distance
Evaluate reaction time measurements Identify anomalies, calculate means and suggest how to make a test fairer. Reaction time
Explain the effect of speed on braking distance A faster vehicle has more kinetic energy, so more work must be done to stop it. Factors affecting braking distance 1
Explain the safety implications of braking distances Lower speeds and bigger gaps are needed in bad conditions and near hazards. Factors affecting braking distance 1
Link speed to the braking force needed A faster vehicle needs a greater braking force to stop in the same distance. Factors affecting braking distance 2
Explain the dangers of large decelerations The brakes may overheat, and the vehicle may skid so the driver loses control. Factors affecting braking distance 2
Calculate momentum For example, 0.16 kg × 25 m/s = 4.0 kg m/s. Momentum is a property of moving objects
Find mass or velocity using p = mv m = p ÷ v and v = p ÷ m. Momentum is a property of moving objects
State the law of conservation of momentum In a closed system, the total momentum before an event equals the total momentum after it. Conservation of momentum
Calculate the total momentum of a system Add the momentum of each object, taking direction into account. Conservation of momentum
Describe evidence that the medium does not travel A floating object bobs up and down as ripples pass but does not move across the water with them. Transverse and longitudinal waves
Rearrange v = f λ with unit conversions Convert kHz, MHz, cm or mm to Hz and m first, then rearrange to find f or λ. Properties of waves
Describe measuring the speed of sound in air Time a sound over a long measured distance, then use speed = distance ÷ time. Properties of waves
Use v = f λ with standard form E.g. find the wavelength of a 100 MHz radio wave using a speed of 3.0 × 10⁸ m/s. Types of electromagnetic waves
Describe the infrared radiation practical Fill a Leslie cube with hot water and measure the infrared from each face with a detector at the same distance. Properties of electromagnetic waves 1
Use radiation dose data to compare risks Compare doses in sieverts or millisieverts: the bigger the dose, the greater the risk of harm. Properties of electromagnetic waves 2
Explain why induced magnetism always attracts The end of the material nearest the magnet becomes the opposite pole to the magnet's pole, so there is always attraction. Poles of a magnet
Define the direction of a magnetic field It is the direction of the force that would act on a north pole placed at that point. Magnetic fields
Compare field strength using field-line spacing Where the field lines are closer together, the field is stronger. Magnetic fields
Use the right-hand grip rule for field direction Point your right thumb along the current (+ to −); your curled fingers show the direction of the field. Electromagnetism
Draw the magnetic field of a solenoid Outside, like a bar magnet's field; inside, strong and uniform (straight, parallel, equally spaced lines). Electromagnetism
Calculate the force with F = BIl Substitute B in tesla, I in amperes and l in metres to get F in newtons. Fleming's left-hand rule (HT only)
Describe how to reverse or speed up motors Reverse the current or the field to reverse it; increase the current, field strength or number of turns to speed it up. Electric motors (HT only)
Find which way a motor coil turns Use Fleming's left-hand rule on each side of the coil to find the forces, then decide clockwise or anticlockwise. Electric motors (HT only)

Grade 7

Grade 7 checklist (PDF)

Compare sizes using orders of magnitude Put both sizes in the same unit, divide, and write the ratio as a power of ten: 1000 times bigger is 3 orders of magnitude. Eukaryotes and prokaryotes
Estimate sizes of sub-cellular structures Compare the structure with the whole cell, e.g. a nucleus a quarter of the width of a 20 µm cell is about 5 µm across. Animal and plant cells
Suggest adaptations of unfamiliar specialised cells Use the same ideas (surface area, mitochondria, shape, missing structures) for a cell you have not studied. Cell specialisation
Suggest how a cell changes as it differentiates It gains the sub-cellular structures its function needs, e.g. more mitochondria or ribosomes, and may change shape. Cell differentiation
Explain how electron microscopes improved understanding Their much higher resolution revealed small sub-cellular structures, such as ribosomes, and the detail inside mitochondria and chloroplasts. Microscopy
Explain why the new cells are identical The DNA is copied exactly, and one copy of every chromosome goes to each new cell. Mitosis and the cell cycle
Interpret data on dividing cells e.g. use the percentage of cells in mitosis to estimate how long mitosis lasts. Mitosis and the cell cycle
Evaluate the use of stem cells Weigh possible treatments against risks such as viral infection, and against ethical or religious objections, then give a conclusion. Stem cells
Explain why large organisms need exchange surfaces Their small surface area to volume ratio and long diffusion distances mean diffusion through the body surface is too slow. Diffusion
Estimate cell concentration from a graph Read the concentration where the line of best fit crosses 0% change in mass. Osmosis
Explain how oxygen affects active transport Less oxygen means less aerobic respiration, so less energy is released and active transport slows. Active transport
Explain why large organisms need organ systems Large organisms have a small surface area to volume ratio, so they need specialised exchange organs and a transport system to supply every cell. Principles of organisation
Explain denaturing by high temperature or pH The active site changes shape, so the substrate no longer fits and the rate of reaction falls. The human digestive system
Calculate rates from the amylase practical Use the equation given, such as rate = 1000 ÷ time taken for the starch to be digested, and compare rates at each pH. The human digestive system
Explain how alveoli are adapted for gas exchange Millions of alveoli give a large surface area, with thin walls and a rich capillary network keeping a steep concentration gradient. The heart and blood vessels
Explain why the left ventricle wall is thicker It pumps blood at a higher pressure all round the body, while the right ventricle only pumps blood to the nearby lungs. The heart and blood vessels
Apply blood functions to unfamiliar situations For example, explain the effects of having too few platelets or too few red blood cells. Blood
Evaluate drugs, devices and transplants Weigh up how well and how quickly each works, risks, side effects, recovery, cost and the need for donors or lifelong drugs, then give a justified conclusion. Coronary heart disease: a non-communicable disease
Evaluate how representative a sample is Large, random samples that include a range of people give data you can apply to the whole population. Health issues
Explain why correlation does not prove causation Another factor might explain the link, so a causal mechanism is needed before saying one factor causes a disease. The effect of lifestyle on some non-communicable diseases
Explain how several factors combine to cause disease Many diseases result from several risk factors interacting, e.g. smoking, poor diet and no exercise together raise heart disease risk. The effect of lifestyle on some non-communicable diseases
Link cancer to the cell cycle Changes to the genes that control cell division make cells divide by mitosis in an uncontrolled way. Cancer
Explain how leaf structure suits photosynthesis Link the thin, broad shape, transparent epidermis, chloroplast position, air spaces, stomata and veins to supplying light, carbon dioxide and water. Plant tissues
Explain how guard cells control water loss Guard cells become turgid to open the stomata and flaccid to close them, balancing gas exchange against water loss. Plant organ system
Explain how water moves through the plant Water evaporates from leaf cells and diffuses out through the stomata, and more water is drawn up the xylem to replace it. Plant organ system
Interpret data on the spread of a disease Describe trends in case numbers, calculate percentage changes and use the way the pathogen spreads to explain the pattern. Communicable (infectious) diseases
Explain how HIV leads to AIDS HIV attacks immune cells; when the immune system is badly damaged, the body cannot deal with other infections or cancers. Viral diseases
Explain why infected leaves must be destroyed Infected leaves, including fallen ones, still carry the fungus, which can spread to healthy leaves by water or wind. Fungal diseases
Explain why controlling mosquitoes controls malaria The protist's life cycle includes the mosquito, so it is normally passed between people only by mosquito bites. Protist diseases
Explain why antibodies are specific Each antibody fits only one antigen, so it binds to only one type of pathogen. Human defence systems
Explain effects of damage to a defence E.g. smoke stops cilia beating, so mucus and pathogens build up in the airways and infections are more likely. Human defence systems
Interpret graphs of antibody concentration After a second exposure, antibodies are made faster and in much larger amounts than after the first. Vaccination
Explain why antibiotic resistance is a concern Resistant strains are not killed by the antibiotic, so infections become hard to treat and the strains can spread. Antibiotics and painkillers
Explain why double blind trials are used Neither doctors nor patients know who has the drug, so their expectations cannot bias the results. Discovery and development of drugs
Explain plant gas exchange in light and dark Plant cells respire all the time, so a plant gives out carbon dioxide in the dark but takes it in overall when photosynthesis is faster than respiration. Photosynthetic reaction
Find the limiting factor on multi-factor graphs (HT) Compare curves: if raising the second factor raises the curve, that factor was limiting the lower curve. Rate of photosynthesis
Use the inverse square law (HT) Light intensity is proportional to 1 ÷ distance², so doubling the distance gives a quarter of the light intensity. Rate of photosynthesis
Explain how nitrate shortage reduces growth Less nitrate means fewer amino acids and less protein, so fewer new cells are made and the plant grows less. Uses of glucose from photosynthesis
Explain why anaerobic respiration transfers less energy The oxidation of glucose is incomplete, so much of the energy stays in the lactic acid or ethanol. Aerobic and anaerobic respiration
Describe how lactic acid is removed (HT) Blood carries lactic acid from the muscles to the liver, where it is converted back into glucose. Response to exercise
Define oxygen debt (HT) The extra oxygen the body needs after exercise to react with the accumulated lactic acid and remove it from the cells. Response to exercise
Explain the importance of the small building blocks Sugars, amino acids, fatty acids and glycerol are what large molecules are built from and broken down into, so they can be reused. Metabolism
Analyse and evaluate reaction time data Calculate means, spot anomalies, judge conclusions and suggest control variables. The human nervous system
Describe how glucagon raises blood glucose Glucagon causes glycogen to be converted into glucose, which is released into the blood. Control of blood glucose concentration
Explain how the four hormones interact E.g. oestrogen inhibits FSH and stimulates LH; progesterone inhibits FSH and LH. Hormones in human reproduction
Give the disadvantages of fertility treatment It is emotionally and physically stressful, success rates are not high, and multiple births are risky. The use of hormones to treat infertility (HT only)
Explain how thyroxine levels are controlled High thyroxine inhibits TSH release from the pituitary, so less thyroxine is released, and the reverse. Feedback systems (HT only)
Compare meiosis with mitosis Compare the number of divisions, the number of cells made, the chromosome number and whether the cells are identical. Meiosis
Discuss the importance of the human genome Explain how each use could benefit people, especially in medicine. DNA and the genome
Construct a genetic cross to make predictions From the information given, work out the genotypes and gametes, draw the Punnett square and give probabilities. Genetic inheritance
Discuss the issues of embryo screening Give economic, social and ethical arguments for and against, using the information provided. Inherited disorders
Explain why the sperm determines sex Eggs always carry X, so the sex depends on whether the sperm carries an X or a Y. Sex determination
Use twin or clone data Identical twins and clones have the same genes, so differences between them are caused by the environment. Variation
Explain how a mutation can change a species A rare new phenotype that suits an environmental change can spread relatively quickly by natural selection. Variation
Compare selective breeding with natural selection In selective breeding humans choose which individuals breed; in natural selection the environment decides which survive to breed. Selective breeding
Evaluate the impact of selective breeding Weigh benefits such as more food against inbreeding and reduced variation. Selective breeding
Describe the main steps of genetic engineering Enzymes isolate the gene, it is inserted into a vector, and the vector puts the gene into the required cells. Genetic engineering
Explain how resistant bacteria show evolution Bacteria reproduce so quickly that natural selection of resistant strains can be seen over a short time. Evidence for evolution
Interpret an evolutionary tree Organisms sharing the most recent common ancestor are the most closely related. Fossils
Explain why variation reduces extinction risk Some individuals are more likely to have characteristics that let them survive the change. Extinction
Suggest causes from information given Use clues in a description or data to name the factor and explain its effect. Extinction
Explain why resistant strains spread People are not immune to the new strain and there is no effective treatment. Resistant bacteria
Explain why new antibiotics won't solve it Developing new antibiotics is costly and slow, so it is unlikely to keep up with new resistant strains. Resistant bacteria
Interpret evolutionary trees Organisms that share the most recent common ancestor are the most closely related. Classification of living organisms
Explain how new evidence changed classification Better microscopes revealed internal structures, and biochemistry revealed chemical differences, leading to new models. Classification of living organisms
Predict knock-on effects of changes in food webs Follow every arrow into and out of the changed species, give a reason for each effect and allow for other food sources. Communities
Explain knock-on effects through a community Show how a change that affects plants then affects the animals that eat them or shelter in them. Abiotic factors
Explain how competition can make a species decline If one species outcompetes another, the other's numbers can fall until too few are left to breed. Biotic factors
Explain adaptations using surface area to volume ratio A large, compact body has a small surface area to volume ratio, so it loses heat more slowly. Adaptations
Explain predator–prey cycles from a graph Prey rise first, giving predators more food; predators rise and eat more prey, so prey fall, then predators fall. Levels of organisation
Explain why the carbon and water cycles matter They return carbon dioxide for photosynthesis and supply fresh water on land, so organisms can grow and survive. How materials are cycled
Compare the stability of two ecosystems Use the numbers of species to explain which is more likely to be badly affected by a change. Biodiversity
Explain how fertiliser run-off kills aquatic life Algae grow, block light, plants die, decomposers respire and use up oxygen, so fish die. Waste management
Explain how using peat releases carbon dioxide Burning peat, or its decay by microorganisms once it is exposed to oxygen, releases carbon dioxide. Land use
Evaluate a decision about land use Weigh people's needs for homes, jobs and materials against the loss of habitats and biodiversity. Land use
Explain how cattle and rice fields add methane Cattle release methane from digestion, and microorganisms in flooded rice fields release methane. Deforestation
Evaluate clearing forest for crops or cattle Weigh food, income and renewable fuel against habitat loss and the carbon dioxide released. Deforestation
Explain how global warming reduces biodiversity Species that cannot adapt or move to suitable areas quickly enough may become extinct. Global warming
Explain conflicting pressures on maintaining biodiversity Conservation costs money and uses land that people also need for food, homes, jobs and income. Maintaining biodiversity
Write ionic equations (Higher tier) Show only the particles that change and leave out spectator ions, e.g. H⁺ + OH⁻ → H₂O. Atoms, elements and compounds
Plan a separation with several steps Combine methods in a sensible order, e.g. dissolve, filter, then crystallise to get pure salt from rock salt. Mixtures
Explain what alpha scattering showed Link each observation (most straight through, some deflected, very few bounced back) to its conclusion about the atom. The development of the model of the atom
Compare sizes using standard form Divide one size by the other, e.g. 1 × 10⁻¹⁰ ÷ 1 × 10⁻¹⁴ = 10 000, and relate the scale to everyday objects. Size and mass of atoms
Calculate A_r for three isotopes Same method with three terms; check that the abundances add up to 100%. Relative atomic mass
Predict reactions from an element's position Use the group's typical reactions and trends, e.g. caesium reacts with water like sodium, but more vigorously. The periodic table
Explain why atomic weight order failed Atomic weight depends on isotopes, so it does not always follow atomic number, e.g. argon and potassium. Development of the periodic table
Describe the whole development in order Early tables, their problems, Mendeleev's changes, the discoveries that confirmed them, then isotopes and atomic number. Development of the periodic table
Explain properties using electronic structure Metal atoms have few outer electrons, which they lose; non-metal atoms gain or share electrons. Metals and non-metals
Explain why reactivity increases down Group 1 The outer electron is further from the nucleus, so it is less strongly attracted and more easily lost. Group 1
Explain why reactivity decreases down Group 7 The outer shell is further from the nucleus, so an electron is attracted less strongly and gained less easily. Group 7
Tell chemical bonds from intermolecular forces Chemical bonds hold atoms or ions together and are strong; intermolecular forces are weak forces between separate molecules. Chemical bonds
Describe electron transfer when the ratio is 2 : 1 For example, in lithium oxide two lithium atoms each transfer one electron to one oxygen atom. Ionic bonding
Give limitations of each type of diagram For example, ball and stick models show gaps and sticks that are not really there; 2D diagrams do not show the 3D arrangement. Ionic compounds
Classify covalent substances as small, large or giant Small molecules (e.g. CH₄), very large molecules (polymers) and giant covalent structures (e.g. diamond, silicon dioxide). Covalent bonding
Draw and label a diagram of metallic bonding Regular rows of positive ions with electrons between them, labelled 'delocalised electrons'. Metallic bonding
Give limitations of the particle model (HT) The model shows particles as solid spheres with no forces between them; real particles are not like this. The three states of matter
Use data and observations to choose state symbols Use melting and boiling points, or words such as 'bubbles', 'precipitate' and 'solution', to decide each state. State symbols
Explain boiling point trends using molecule size Larger molecules have stronger intermolecular forces, so they have higher melting and boiling points. Properties of small molecules
Compare intermolecular forces with covalent bonds Covalent bonds are strong and intermolecular forces are weak, which explains the bulk properties of molecular substances. Properties of small molecules
Tell polymers from giant covalent structures Polymers are separate chain molecules with forces between them; a giant covalent structure is one continuous network of covalent bonds. Polymers
Contrast giant covalent and small molecular substances Melting a giant structure breaks covalent bonds; melting small molecules only overcomes intermolecular forces. Giant covalent structures
Interpret diagrams of pure metals and alloys Regular layers of identical atoms compared with layers disrupted by atoms of a different size. Properties of metals and alloys
Compare conduction in metals and ionic compounds Metals conduct when solid because electrons move; ionic compounds conduct only when molten or dissolved, because ions move. Metals as conductors
Link diamond's properties to its uses Its hardness and very high melting point make it useful for cutting tools and drill tips. Diamond
Describe carbon nanotubes and their properties Cylindrical fullerenes with a very high length to diameter ratio; very strong and conduct electricity. Graphene and fullerenes
Balance equations with brackets in formulae Count atoms inside brackets carefully, e.g. Ca(OH)₂ + 2HNO₃ → Ca(NO₃)₂ + 2H₂O. Conservation of mass and balanced chemical equations
Show that M_r values balance in equations The total M_r of the reactants (using balancing numbers) equals the total M_r of the products. Relative formula mass
Explain mass changes using the particle model Gas particles move quickly and randomly and spread out, so they leave an open container or reach the reactants from the air. Mass changes when a reactant or product is a gas
Write a mean with its uncertainty Give the mean ± uncertainty with a unit, e.g. 24.3 ± 0.2 cm³. Chemical measurements
Calculate mass from moles mass (g) = moles × M_r. Moles (HT only)
Calculate product mass from reactant mass Moles of known substance → mole ratio → moles of wanted substance → mass. Amounts of substances in equations (HT only)
Find the simplest whole-number mole ratio Divide every number of moles by the smallest one. Using moles to balance equations (HT only)
Write the balanced equation from the ratio The whole numbers are the balancing numbers in front of each formula. Using moles to balance equations (HT only)
Identify the limiting reactant using moles Divide the moles of each reactant by its balancing number; the smallest value is limiting. Limiting reactants (HT only)
Explain how mass and volume affect concentration (HT) More solute in the same volume, or the same solute in less volume, gives a higher concentration. Concentration of solutions
Explain why a reaction is a redox reaction Show that one substance gains oxygen while another loses oxygen in the same reaction. Metal oxides
Link reactivity to forming positive ions The more easily a metal's atoms lose electrons to form positive ions, the more reactive the metal is. The reactivity series
Evaluate an unfamiliar extraction method Use the information given and the reactivity series to judge a method on energy, cost, raw materials and waste. Extraction of metals and reduction
Write half equations for displacement reactions For example, Mg → Mg²⁺ + 2e⁻ and Cu²⁺ + 2e⁻ → Cu. Oxidation and reduction in terms of electrons (HT only)
Explain these reactions as redox reactions The metal atoms lose electrons (oxidised) and the hydrogen ions gain electrons (reduced). Reactions of acids with metals
Write balanced equations for neutralisation reactions For example, CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂. Neutralisation of acids and salt production
Choose suitable reactants for a named salt Pick the acid with the right negative ion and an insoluble compound of the metal (or a metal that is safe to use). Soluble salts
Explain why a stronger acid has lower pH At the same concentration, a strong acid releases more H⁺ ions, so its pH is lower. Strong and weak acids (HT only)
Explain what happens when ions are discharged At the electrodes, ions gain or lose electrons and become atoms or molecules of elements. The process of electrolysis
Write half equations for molten electrolysis For example, Pb²⁺ + 2e⁻ → Pb and 2Br⁻ → Br₂ + 2e⁻. Electrolysis of molten ionic compounds
Explain why the anodes must be replaced Oxygen formed at the carbon anodes reacts with them to form carbon dioxide, so they wear away. Using electrolysis to extract metals
Plan the required practical investigation Use inert electrodes and a d.c. supply, identify each product, and compare solutions to test a hypothesis. Electrolysis of aqueous solutions
Write the half equation for hydrogen 2H⁺ + 2e⁻ → H₂. Representation of reactions at electrodes as half equations (HT only)
Suggest and explain improvements to the practical For example, a lid and extra insulation reduce energy transfer to the surroundings, and repeats let you calculate a mean. Energy transfer during exothermic and endothermic reactions
Explain why some reactions need heating to start Particles must collide with at least the activation energy, so energy (e.g. a spark or flame) must be supplied at first. Reaction profiles
Calculate the energy change for a simple reaction Overall energy change = energy to break bonds − energy released making bonds, e.g. for H₂ + Cl₂ → 2HCl. The energy change of reactions (HT only)
Calculate the gradient of a tangent (HT) Rate at that time = change in y ÷ change in x, using two points far apart on the tangent. Calculating rates of reactions
Calculate a mean rate in mol/s (HT) Convert a mass to moles with moles = mass ÷ M_r (or A_r), then divide by the time in seconds. Calculating rates of reactions
Calculate surface area to volume ratio For a cube, surface area = 6 × side² and volume = side³; smaller pieces have a larger ratio. Collision theory and activation energy
Link catalysis to successful collisions With a lower activation energy, more collisions have enough energy to react, so successful collisions are more frequent. Catalysts
Explain how the rates change before equilibrium The forward rate falls as reactants are used up and the reverse rate rises as products build up, until they are equal. Equilibrium
Predict the effect of a change in conditions Use the information given (equation, energy change, numbers of molecules) to say which way the position shifts. The effect of changing conditions on equilibrium (HT only)
Explain shifts using Le Chatelier's principle The system counteracts the change by using up an added substance or replacing a removed one. The effect of changing concentration (HT only)
Explain temperature effects using Le Chatelier Increasing the temperature favours the endothermic direction, which takes in energy. The effect of temperature changes on equilibrium (HT only)
Deduce the energy change from yield data If the yield falls as the temperature rises, the forward reaction is exothermic. The effect of temperature changes on equilibrium (HT only)
Recognise when pressure has no effect If both sides have the same number of gas molecules, changing the pressure does not move the position. The effect of pressure changes on equilibrium (HT only)
Explain pressure effects using Le Chatelier Fewer molecules exert a lower pressure, so shifting to that side counteracts a pressure increase. The effect of pressure changes on equilibrium (HT only)
Work out an alkane's formula from its Mr M_r = 14n + 2, so solve for n: an M_r of 72 gives n = 5, which is C₅H₁₂. Crude oil, hydrocarbons and alkanes
Explain why there are so many carbon compounds Carbon atoms can bond to each other to form chains of different lengths, making families of similar compounds. Fractional distillation and petrochemicals
Explain the boiling point trend using intermolecular forces Larger molecules have stronger forces between the molecules, so more energy is needed to overcome them. Properties of hydrocarbons
Compare data to rank samples by purity The purer sample melts closer to the pure value and over a narrower range of temperatures. Pure substances
Predict effects of changing a formulation Changing the amount of one component changes the properties of the product, so it may no longer do its job. Formulations
Explain how chromatography separates substances Each substance is distributed differently between the mobile and stationary phases, so each moves a different distance. Chromatography
Use different solvents to test purity A pure compound gives a single spot in every solvent; a mixture may only separate in some solvents. Chromatography
Explain why limewater turns milky Carbon dioxide reacts with calcium hydroxide to form insoluble calcium carbonate, a white precipitate. Test for carbon dioxide
Calculate percentage oxygen from experimental results Divide the decrease in gas volume, when oxygen is removed by a reaction, by the starting volume and multiply by 100. The proportions of different gases in the atmosphere
Use given evidence to evaluate a theory Say which evidence supports the theory, which does not, and why the evidence is uncertain, then give a conclusion. The Earth's early atmosphere
Balance the symbol equation for photosynthesis The balanced equation is 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. How oxygen increased
Explain how these deposits removed carbon dioxide The carbon in the organisms came from carbon dioxide, and burying them locked it away for millions of years. How carbon dioxide decreased
Explain why more greenhouse gases cause warming More long wavelength radiation is absorbed and re-emitted towards the Earth, so less escapes to space and the average temperature rises. Greenhouse gases
Describe uncertainties in climate evidence The climate is complex, so models are simplified, data about the past are incomplete and future emissions are unknown. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Explain effects on food production and wildlife Changes in temperature and rainfall change where crops grow well and where species can survive. Global climate change
Calculate and compare emissions from data Use given data, e.g. grams of carbon dioxide per km × distance, and convert units correctly. The carbon footprint and its reduction
Write balanced equations for combustion For example, 2CH₄ + 3O₂ → 2CO + 4H₂O for incomplete combustion of methane. Atmospheric pollutants from fuels
Explain why carbon monoxide is toxic It combines with haemoglobin in red blood cells, so the blood carries less oxygen. Properties and effects of atmospheric pollutants
Interpret resource data from charts and tables Read values, describe trends and calculate, for example how many years a reserve will last. Using the Earth's resources and sustainable development
Compare treating ground water and salty water Ground water only needs filtering and sterilising; salty water must be desalinated, which needs large amounts of energy. Potable water
Calculate dissolved solids from practical results Mass of dried residue ÷ volume of the sample, e.g. in g/dm³ after converting cm³ to dm³. Potable water
Compare treating waste, ground and salt water Ground water needs the least treatment; waste water needs many stages; salt water needs desalination, which uses large amounts of energy. Waste water treatment
Explain displacement and electrolysis of copper compounds Iron is more reactive than copper; at the negative electrode Cu²⁺ + 2e⁻ → Cu. Alternative methods of extracting metals (HT only)
Explain why LCAs are not fully objective Giving numerical values to the effects of pollutants needs value judgements. Life cycle assessment
Evaluate a recycling scheme from given data Balance the resources and energy saved against the energy and cost of collecting, transporting and sorting. Ways of reducing the use of resources
Use calculations to compare energy stores Calculate the energy in each store before and after a change to show how the total energy is shared out. Energy stores and systems
Rearrange to find speed, height or extension E.g. h = E_p ÷ (m × g), or v = √(2E_k ÷ m), taking the square root last. Changes in energy
Explain why the measured value is too high Energy is dissipated to the surroundings, so more energy is supplied than the block gains. Energy changes in systems
Combine power with work done or energy Find the work done or gravitational potential energy gained first, then divide by the time. Power
Rearrange to find the input or output Useful output = efficiency × total input; total input = useful output ÷ efficiency. Efficiency
Describe ways to increase efficiency Reduce the wasted transfers, e.g. lubricate moving parts, streamline, insulate (Higher tier only). Efficiency
Explain trends in energy resource use Use data and reasons such as cutting carbon dioxide emissions and the falling cost of renewables. National and global energy resources
Analyse resistance against length results A straight line through the origin shows resistance is directly proportional to length. Current, resistance and potential difference
Find resistance at a point on I–V graph Read V and I at that point and use R = V ÷ I, not the gradient. Resistors
Explain thermistor and LDR sensing circuits Link a change in temperature or light to a change in resistance, current and the pd across each component. Resistors
Solve multi-step series circuit problems Find the total resistance, then I = V ÷ R, then the pd across each resistor with V = I R. Series and parallel circuits
Find frequency from a pd–time graph Read the time for one complete cycle and use frequency = 1 ÷ time period. Direct and alternating potential difference
Explain why touching the live wire is dangerous Your body is at 0 V, so there is a large pd across you and a current flows through you. Mains electricity
Explain dangers even when a switch is open The live wire is still connected to the supply, so it is still at about 230 V. Mains electricity
Find current or resistance from P = I² R Use I = √(P ÷ R) or R = P ÷ I². Power
Combine E = Q V with Q = I t Find the charge first, then the energy, in multi-step problems. Energy transfers in everyday appliances
Explain why the National Grid is efficient A lower current means less heating of the cables, so less energy is wasted. The National Grid
Solve multi-step density problems For example, find a volume from dimensions in cm, convert it to m³, then use a density in kg/m³ to find the mass. Density of materials
Explain energy changes during a change of state The energy supplied increases the potential energy of the particles, so internal energy rises but the temperature does not. Internal energy
Use heater power and time in calculations Find the energy supplied with E = P t, then use it in ΔE = m c Δθ. Temperature changes in a system and specific heat capacity
Explain why a measured c is too high Energy is transferred to the surroundings, so the temperature rise is smaller and c = ΔE ÷ (m Δθ) comes out larger. Temperature changes in a system and specific heat capacity
Do multi-step heating and melting calculations Work out each stage separately with ΔE = m c Δθ or E = m L, then add the energies. Changes of state and specific latent heat
Apply the particle model to real situations For example, explain why a sealed can may burst if heated, or why tyre pressure falls on a cold night. Particle motion in gases
Identify isotopes and ions from data Use particle numbers in a table to decide which atoms are isotopes of the same element and which particles are charged. Mass number, atomic number and isotopes
Explain why the plum pudding model was replaced It predicted only tiny deflections, so large deflections needed a new model with a concentrated, charged nucleus. The development of the model of the atom
Explain how new evidence changes models When experiments give results a model cannot explain, scientists change or replace the model. The development of the model of the atom
Choose the best radiation for a use Justify the choice using penetration and ionising power, and say why the others are unsuitable. Radioactive decay and nuclear radiation
Identify the decay type from an equation Compare the mass and atomic numbers before and after to see what was emitted. Nuclear equations
Correct count rates for background radiation Subtract the background count rate from each reading before finding the half-life. Half-lives and the random nature of radioactive decay
Explain which radiation is most hazardous where Outside the body beta and gamma are more hazardous; inside the body alpha is most hazardous. Radioactive contamination
Explain scalar–vector pairs such as speed and velocity Two objects can have the same speed but different velocities if they move in different directions. Scalar and vector quantities
Use the proportionality between weight and mass W ∝ m, so a graph of weight against mass is a straight line through the origin with a gradient equal to g. Gravity
Find a resultant using a scale drawing Draw the two forces tip-to-tail to scale; the resultant is the arrow from the start of the first to the end of the second. Resultant forces
Link work done to changes in energy stores Work done by brakes equals the kinetic energy lost; work done lifting an object equals its gain in gravitational potential energy. Work done and energy transfer
Calculate elastic potential energy stored Use E_e = 0.5 × k × e², up to the limit of proportionality. Forces and elasticity
Link work done to energy stored If the spring is not inelastically deformed, the work done stretching it equals the elastic potential energy stored. Forces and elasticity
Find the displacement for a right-angled journey Use a scale drawing (or Pythagoras): 30 m north then 40 m east is 50 m at about 53° east of north. Distance and displacement
Estimate speeds, distances and times For example, walking 1 km at ~1.5 m/s takes about 670 s, roughly 11 minutes. Speed
Explain circular motion: constant speed, changing velocity The direction of motion changes all the time, so the velocity changes even though the speed stays the same. Velocity
Recognise acceleration and deceleration on the graph A curve getting steeper shows acceleration; a curve getting less steep shows deceleration. The distance–time relationship
Estimate the size of everyday accelerations For example, a car reaching 30 m/s in about 10 s accelerates at about 3 m/s². Acceleration
Find distance from area under v–t graph Split the area into rectangles and triangles and add them. Acceleration
Define and use the idea of inertia Inertia is the tendency of objects to continue in their state of rest or of uniform motion. Newton's First Law
Estimate forces in everyday road transport For example, a car of mass ~1000 kg decelerating at ~6 m/s² needs ~6000 N. Newton's Second Law
Distinguish Third Law pairs from balanced forces Balanced forces act on the same object; a Third Law pair acts on two different objects. Newton's Third Law
Apply the Third Law to equilibrium situations A book on a table pushes down on the table, and the table pushes up on the book with an equal force. Newton's Third Law
Interpret stopping distance data and graphs Thinking distance rises in proportion to speed; braking distance rises more and more steeply. Stopping distance
Evaluate factors affecting thinking distance from data Compare thinking distances with and without a factor, at the same speed. Reaction time
Estimate stopping distances at typical speeds A car on a dry road needs roughly 25 m to stop from 13 m/s and roughly 100 m from 31 m/s. Factors affecting braking distance 1
Calculate a braking force from kinetic energy Braking force × braking distance = ½ m v². Factors affecting braking distance 2
Explain that momentum is a vector Momentum has the same direction as the velocity; opposite directions have opposite signs. Momentum is a property of moving objects
Compare the momentum of different objects A slow, heavy object can have more momentum than a fast, light one. Momentum is a property of moving objects
Calculate the velocity after objects join Total momentum before = (m₁ + m₂) × v after. Conservation of momentum
Explain explosions and recoil using momentum The total momentum is zero before, so the parts move apart with equal and opposite momentum. Conservation of momentum
Explain what a closed system is No external forces act on the system, so its total momentum cannot change. Conservation of momentum
Explain how particles move in a sound wave Air particles vibrate backwards and forwards about fixed positions, parallel to the direction of travel, passing energy on to their neighbours. Transverse and longitudinal waves
Describe the ripple tank and string practical Measure across several wavelengths, find the frequency, use v = f λ, and explain why the apparatus suits each measurement. Properties of waves
Explain why higher frequency means shorter wavelength All EM waves have the same speed, so a higher frequency means a proportionally shorter wavelength. Types of electromagnetic waves
Explain refraction using wave fronts (HT) The part of a wave front that reaches the slower medium first slows down first, so the wave front changes direction. Properties of electromagnetic waves 1
Explain how radio waves are produced (HT) Oscillations (an alternating current) in an electrical circuit produce radio waves of the same frequency. Properties of electromagnetic waves 2
Explain why microwaves suit satellite communications (HT) Microwaves pass through the Earth's atmosphere, so they can reach satellites in space. Uses and applications of electromagnetic waves
Explain why X-rays suit imaging bones (HT) X-rays pass through soft tissue but are absorbed by bone, so bones show up on the image. Uses and applications of electromagnetic waves
Explain how to test for a magnet Only repulsion proves an object is a permanent magnet, because a magnetic material is attracted to both poles. Poles of a magnet
Explain the compass evidence for Earth's magnetic core A compass lines up in a fixed direction even far from any magnet, so the Earth must have a magnetic field, which comes from its core. Magnetic fields
Explain how solenoids and iron cores strengthen fields The fields of all the turns add together inside the coil, and an iron core becomes magnetised, making the field much stronger. Electromagnetism
Rearrange F = BIl after converting units e.g. find B in tesla when the length is given in mm or cm. Fleming's left-hand rule (HT only)
Explain the role of the split-ring commutator It reverses the current in the coil every half turn, so the coil keeps turning in the same direction. Electric motors (HT only)

Grade 8

Grade 8 checklist (PDF)

Give real sizes in standard form e.g. a real size of 0.000012 m is 1.2 × 10⁻⁵ m. Microscopy
Evaluate the benefits and drawbacks of vaccination Weigh the protection of individuals and populations against the fact that vaccines do not always work and can cause mild side effects. Vaccination
Evaluate greenhouse costs against extra yield (HT) Use data to decide whether the value of the extra crop from adding heat, light or carbon dioxide is more than the extra cost. Rate of photosynthesis
Explain fast breathing after exercise (HT) Breathing and heart rate stay high to supply the extra oxygen needed to repay the oxygen debt. Response to exercise
Explain insulin and glucagon in negative feedback The two hormones act in opposite directions, returning glucose to normal whenever it rises or falls. Control of blood glucose concentration
Explain why the cycle restarts without pregnancy Progesterone falls, the lining breaks down, and FSH is no longer inhibited, so another egg matures. Hormones in human reproduction
Evaluate IVF from different points of view Weigh benefits against risks for patients and doctors, including ethical issues such as unused embryos. The use of hormones to treat infertility (HT only)
Interpret simple negative feedback diagrams Follow the arrows to predict and explain what happens when a hormone level rises or falls. Feedback systems (HT only)
Deduce genotypes from family tree evidence For example, two unaffected parents with an affected child must both be heterozygous. Genetic inheritance
Evaluate embryo screening with a justified conclusion Weigh the benefits against the costs and concerns, and make a judgement supported by the information. Inherited disorders
Apply natural selection to unfamiliar examples Use the details given (predators, climate, food) in a logical chain of cause and effect. Evolution
Evaluate genetic engineering in agriculture and medicine Weigh the benefits against the risks and objections to reach a justified conclusion. Genetic engineering
Explain unfamiliar adaptations from given information Use the description or data to link each feature to a specific survival problem in that habitat. Adaptations
Evaluate a conservation method using given data Weigh the evidence of success against costs and limitations, then reach a justified conclusion. Maintaining biodiversity
Write half equations (Higher tier) Show the electrons lost or gained by one substance, with atoms and charges balanced, e.g. Cl₂ + 2e⁻ → 2Cl⁻. Atoms, elements and compounds
Find an unknown abundance from A_r Call one abundance x and the other (100 − x), then solve the equation. Relative atomic mass
Write ionic equations for displacement (Higher tier) Leave out the spectator metal ions, e.g. Cl₂ + 2I⁻ → 2Cl⁻ + I₂. Group 7
Give limitations of each type of diagram For example, dot and cross diagrams and displayed formulae do not show the 3D shape of a molecule. Covalent bonding
Compare melting points using the charges on ions Ions with bigger charges (e.g. Mg²⁺ and O²⁻) attract each other more strongly, so more energy is needed to separate them. Properties of ionic compounds
Compare the structures and properties of diamond and graphite Four bonds in a rigid 3D network compared with three bonds, layers and delocalised electrons. Graphite
Explain why C₆₀ has a lower melting point C₆₀ is molecular, so melting overcomes weak intermolecular forces, not covalent bonds. Graphene and fullerenes
Balance ionic and half equations (HT) Atoms and total charge must both be equal on each side, e.g. Cu²⁺ + 2e⁻ → Cu. Conservation of mass and balanced chemical equations
Use M_r to identify an unknown element Work backwards, e.g. if XCl₂ has M_r 111, X = 111 − 71 = 40, so X is calcium. Relative formula mass
Predict the size of a mass change (HT) Use moles, e.g. 100 g (1 mol) of CaCO₃ loses 44 g (1 mol) of CO₂ when heated. Mass changes when a reactant or product is a gas
Use uncertainties to compare sets of results A smaller uncertainty means more precise results; check whether a value lies within mean ± uncertainty. Chemical measurements
Calculate numbers of particles number of particles = moles × 6.02 × 10²³. Moles (HT only)
Calculate the reactant mass needed Start from the mass of product you want and work back through the mole ratio. Amounts of substances in equations (HT only)
Turn a non-whole ratio into whole numbers If you get 1 : 1.5, multiply every number by 2 to get 2 : 3. Using moles to balance equations (HT only)
Calculate product mass from the limiting reactant Use only the moles of the limiting reactant in the reacting-mass method. Limiting reactants (HT only)
Solve multi-step concentration problems Rearrange the equation, e.g. find the volume of solution that contains a given mass. Concentration of solutions
Write ionic equations for displacement reactions Leave out the spectator ions, e.g. Mg + Cu²⁺ → Mg²⁺ + Cu. Oxidation and reduction in terms of electrons (HT only)
Write ionic and half equations for them For example, Mg + 2H⁺ → Mg²⁺ + H₂, with the acid's negative ion left out as a spectator. Reactions of acids with metals
Relate pH changes to H⁺ concentration Each decrease of 1 pH unit means the H⁺ concentration is 10 times greater. Strong and weak acids (HT only)
Write half equations for aluminium extraction Al³⁺ + 3e⁻ → Al at the cathode and 2O²⁻ → O₂ + 4e⁻ at the anode. Using electrolysis to extract metals
Explain which ions remain in solution Ions that are not discharged stay behind, e.g. Na⁺ and OH⁻ ions form sodium hydroxide solution. Electrolysis of aqueous solutions
Write the half equation for oxygen From hydroxide ions in solution: 4OH⁻ → O₂ + 2H₂O + 4e⁻. Representation of reactions at electrodes as half equations (HT only)
Complete and balance supplied half equations Balance the atoms first, then add electrons so the total charge is equal on both sides. Representation of reactions at electrodes as half equations (HT only)
Explain why exothermic reactions keep going once started The energy released gives more particles at least the activation energy, so the reaction continues without further heating. Reaction profiles
Calculate energy changes involving many bonds Multiply each bond energy by the number of bonds in a molecule and by the balancing number, e.g. for a combustion reaction. The energy change of reactions (HT only)
Plan a rates investigation from a hypothesis Give a testable hypothesis, a step-by-step method with a range of values and repeats, and say how the results test it. Factors which affect the rates of chemical reactions
Use proportionality to predict changes in rate E.g. doubling the concentration doubles the frequency of collisions, so the rate doubles. Collision theory and activation energy
Explain a prediction fully using Le Chatelier Say what the change is, how the system counteracts it, which way the position shifts and what happens to the product. The effect of changing conditions on equilibrium (HT only)
Interpret colour changes and given data Use the colours or concentrations in the question to decide which way the position moved. The effect of changing concentration (HT only)
Describe all concentration changes after a disturbance An added substance falls a little but stays higher than before; the other concentrations change until constant again. The effect of changing concentration (HT only)
Explain colour changes caused by temperature Link the direction of the shift to the colour of the substance that increases. The effect of temperature changes on equilibrium (HT only)
Weigh yield against rate when choosing temperature A lower temperature gives more product for an exothermic reaction, but the rate is slower. The effect of temperature changes on equilibrium (HT only)
Use pressure data to test an equation E.g. if the yield rises with pressure, the product side must have fewer gas molecules. The effect of pressure changes on equilibrium (HT only)
Describe the atmosphere's main changes and causes Write a logically ordered account linking each change in carbon dioxide, oxygen and nitrogen to its cause. How carbon dioxide decreased
Evaluate a model of the greenhouse effect Compare an experiment or model with the real atmosphere and judge what it does and does not show. Greenhouse gases
Evaluate the quality of a climate report Judge the amount of data, how it was collected, peer review, possible bias and whether the conclusion fits the evidence. Human activities which contribute to an increase in greenhouse gases in the atmosphere
Discuss scale, risk and environmental implications Weigh how widespread, how likely and how serious an effect is, and who is least able to adapt. Global climate change
Evaluate ways to reduce a carbon footprint Weigh how much each action saves, its cost and its limitations to reach a justified judgement. The carbon footprint and its reduction
Predict combustion products from fuel information Use the elements in the fuel and the conditions (oxygen supply, temperature) to predict and explain every product. Atmospheric pollutants from fuels
Use orders of magnitude to judge data Compare powers of ten (10⁹ is a thousand times 10⁶) to decide whether a difference is significant. Using the Earth's resources and sustainable development
Evaluate biological extraction methods using given data Weigh up using low-grade ores without digging up rock against slow rates, small yields and possible pollution. Alternative methods of extracting metals (HT only)
Explain how selective LCAs can be misused Leaving out stages or impacts can support a conclusion decided in advance, for example in advertising. Life cycle assessment
Link energy stores in multi-step problems Use 'energy lost from one store = energy gained by another' to find a speed or a height. Changes in energy
Find c from a temperature–time graph With a heater of constant power P, the gradient is P ÷ (m × c), so c = P ÷ (m × gradient). Energy changes in systems
Evaluate energy resources using data Weigh up reliability, cost and environmental impact, then give a conclusion with a reason. National and global energy resources
Solve parallel problems using branch currents Each branch has the full supply pd; find each branch current with I = V ÷ R and add them. Series and parallel circuits
Combine power equations with V = I R Link P = V I, P = I² R and V = I R in multi-step problems. Power
Calculate power wasted in transmission cables Find the current with I = P ÷ V, then the heating loss with P = I² R. The National Grid
Find specific latent heat from experimental data Use E = P t for the energy supplied and the mass that changed state, then L = E ÷ m. Changes of state and specific latent heat
Link ionising power to range The more strongly a radiation ionises, the faster it loses energy, so the shorter its range. Radioactive decay and nuclear radiation
Work through a chain of decays Apply several alpha and beta decays in turn to find the final nucleus. Nuclear equations
Find the net decline as a ratio After n half-lives, (1/2)ⁿ of the original remains, so the net decline is the rest (Higher tier). Half-lives and the random nature of radioactive decay
Resolve a force into two perpendicular components Draw the force to scale and complete a right-angled triangle to measure its horizontal and vertical components. Resultant forces
Use vector diagrams for equilibrium If three forces are in equilibrium, their arrows drawn tip-to-tail form a closed triangle. Resultant forces
Link changing velocity to acceleration and force A changing velocity is an acceleration, so there must be a resultant force on the object. Velocity
Find speed at an instant using a tangent Draw a tangent to the curve at that time and calculate its gradient. The distance–time relationship
Count squares to find area under curves Count the squares under a curved line and multiply by the distance one square represents. Acceleration
Explain inertial mass Inertial mass is a measure of how difficult it is to change an object's velocity: force ÷ acceleration. Newton's Second Law
Explain why braking distance increases fastest For the same braking force, braking distance is proportional to speed squared, because kinetic energy is. Stopping distance
Calculate a reaction time from ruler-drop distance Use v² − u² = 2 a s with a = 9.8 m/s² to find v, then t = v ÷ a. Reaction time
Explain why braking distance depends on speed squared Braking force × braking distance = ½ m v², so for a constant force, distance ∝ v². Factors affecting braking distance 1
Estimate braking forces for typical road vehicles Use typical masses and speeds with F = m a or work done = kinetic energy. Factors affecting braking distance 2
Calculate a change in momentum, including direction For a rebound, change in momentum = m v − m u with the correct signs. Momentum is a property of moving objects
Solve collisions with objects moving in opposite directions Use + and − for direction; the sign of the answer gives the direction of motion. Conservation of momentum
Explain how radio waves are received (HT) Radio waves absorbed by an aerial can induce an alternating current with the same frequency as the waves. Properties of electromagnetic waves 2
Explain why gamma rays treat cancer (HT) Gamma rays are ionising and carry a lot of energy, so a carefully aimed beam can kill cancer cells. Uses and applications of electromagnetic waves
Predict how changes affect the force e.g. reversing both the current and the field leaves the direction unchanged; doubling I and halving l leaves F unchanged. Fleming's left-hand rule (HT only)
Explain why the coil keeps turning past vertical When the coil is vertical the forces give no turning effect, but its momentum carries it past, just as the commutator reverses the current. Electric motors (HT only)

Grade 9

Grade 9 checklist (PDF)

Find M_r from mass and moles M_r = mass ÷ moles, then use it to identify a substance or element. Moles (HT only)
Scale reacting masses in kilograms or tonnes Mass ratios work in any unit as long as you use the same unit throughout. Amounts of substances in equations (HT only)
Find a missing mass, then balance Use conservation of mass to find the unknown mass before converting all masses to moles. Using moles to balance equations (HT only)
Calculate the mass of excess reactant left Moles left over = moles at the start − moles that reacted; then convert to a mass. Limiting reactants (HT only)
Balance ionic equations with different ion charges Match the electrons lost and gained, e.g. 2Al + 3Cu²⁺ → 2Al³⁺ + 3Cu. Oxidation and reduction in terms of electrons (HT only)
Separate strength from concentration in unfamiliar data For example, explain why a concentrated weak acid can have a lower pH than a very dilute strong acid. Strong and weak acids (HT only)
Calculate an unknown bond energy Put the known values into overall energy change = bonds broken − bonds made and rearrange to find the missing bond energy. The energy change of reactions (HT only)

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