5.9.3.2Properties and effects of atmospheric pollutants
AQA GCSE Combined Science (8464), Higher tier · Chemistry › Chemistry of the atmosphere › Common atmospheric pollutants and their sources
Practise Properties and effects of atmospheric pollutants. 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
The problems caused by carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates in the air. Expect 1 to 3 mark 'give' and 'explain' questions, data questions on pollution levels, and 6-mark answers that link each pollutant to how it forms and the problems it causes.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
3
State that carbon monoxide is toxicCarbon monoxide is a toxic (poisonous) gas.
4
Name the gases that cause acid rainSulfur dioxide and oxides of nitrogen cause acid rain.
4
Give effects of acid rainIt damages buildings and statues, harms trees and plants, and makes lakes acidic, harming aquatic life.
5
Explain why carbon monoxide is hard to detectIt is colourless and odourless, so you cannot see or smell it.
6
Explain how particulates cause global dimmingParticulates reflect sunlight back into space, so less sunlight reaches the Earth's surface.
6
Describe the health effects of these pollutantsSulfur dioxide and oxides of nitrogen cause respiratory problems, and particulates can damage the lungs.
7
Explain why carbon monoxide is toxicIt combines with haemoglobin in red blood cells, so the blood carries less oxygen.
Notes
Carbon monoxide
Carbon monoxide, CO, is a toxic gas.
It is colourless and odourless, so it is not easily detected. People can be poisoned without knowing, which is why homes with fuel-burning boilers, fires or stoves should have carbon monoxide alarms.
It is toxic because it combines with haemoglobin in red blood cells, so the blood can carry less oxygen around the body. This can cause drowsiness, unconsciousness and death. grade 7+
Sulfur dioxide and oxides of nitrogen
Both cause respiratory problems in humans, e.g. breathing difficulties, and can make asthma worse.
Both cause acid rain: they dissolve in water droplets in clouds to form acidic solutions, which fall as rain.
Acid rain damages buildings and statues, especially those made of limestone, which reacts with acids. It also corrodes metals.
Acid rain damages trees and other plants, and makes lakes and rivers more acidic, which can kill fish and other aquatic life.
Particulates
Particulates are tiny solid particles, such as soot, and unburned hydrocarbons in the air.
They cause global dimming: they reflect sunlight back into space, so less sunlight reaches the Earth's surface.
They cause health problems: very small particles can be breathed deep into the lungs, damaging them and causing breathing problems.
Linking source to effect
Carbon monoxide: from incomplete combustion; toxic and hard to detect.
Sulfur dioxide: from sulfur in the fuel; acid rain and respiratory problems.
Oxides of nitrogen: from nitrogen and oxygen in the air at high temperature; acid rain and respiratory problems.
Particulates: from incomplete combustion and unburned fuel; global dimming and health problems.
Cheatsheet
Carbon monoxide: toxic, colourless and odourless, so not easily detected
Sulfur dioxide and oxides of nitrogen: respiratory problems and acid rain
Acid rain: damages buildings and statues, harms trees and plants, acidifies lakes (kills aquatic life)
Particulates: global dimming and health problems (lung damage)
Global dimming: particulates reflect sunlight, so less reaches the Earth's surface
Carbon monoxide combines with haemoglobin, so the blood carries less oxygen grade 7+
How to answer each type of question
Recall a property or effect of a pollutant
1 to 3 marks4
Match the pollutant to its problem: CO toxic; SO2 and NOx acid rain and breathing problems; particulates global dimming and health problems.
Give the specific property asked for, e.g. 'colourless' or 'odourless'.
Example. (a) Give one property of carbon monoxide that makes it difficult to detect. (b) Name two pollutants that cause acid rain.
Say the gas dissolves in water in clouds to form acid rain.
Name what is damaged: buildings and statues, trees and plants, lakes and aquatic life.
Say how, e.g. the acid reacts with limestone.
Example. A coal-burning power station releases sulfur dioxide. Describe how this can damage a forest and a limestone building many kilometres away.
Show the model answer
The sulfur dioxide is carried by the wind and dissolves in water droplets in clouds (1), forming acid rain (1). The acid rain damages or kills the trees (1) and reacts with the limestone, wearing away the building (1).
Explain why a pollutant is dangerous
2 to 3 marks7
State the problem (e.g. toxic).
Explain how it harms the body (e.g. haemoglobin carries less oxygen).
Explain why the danger is hard to notice or avoid (e.g. colourless and odourless).
Example. Explain why a faulty gas boiler that produces carbon monoxide is dangerous, and why people are advised to fit a carbon monoxide alarm.
Show the model answer
Carbon monoxide is toxic (1). It combines with haemoglobin in the blood, so the blood carries less oxygen (1). It is colourless and odourless, so people cannot tell it is there without an alarm (1).
Use data about a pollutant
3 to 4 marks7
Percentage change = change ÷ original value × 100.
Round as the question asks.
Link the change to a problem the pollutant causes.
Example. The mean concentration of particulates beside a busy road was 42 μg/m3. After a clean air zone was introduced, it fell to 30 μg/m3. (a) Calculate the percentage decrease. Give your answer to 2 significant figures. (b) Suggest one benefit to people's health. (c) Explain how particulates cause global dimming.
Show the model answer
(a) (42 − 30) ÷ 42 × 100 (1) = 29% (1) (b) Fewer particles are breathed into people's lungs, so fewer breathing problems or less lung damage (1) (c) Particulates reflect sunlight (1), so less sunlight reaches the Earth's surface (1)
Shortcuts and memory tricks
Carbon monoxide is the 'silent killer': no colour, no smell.
Acid rain gases are the 'S and N' pair: sulfur dioxide and nitrogen oxides.
Particulates: 'Dim and Damage': global dimming and damage to lungs.
Learn one problem per pollutant first, then add the detail (why or how).
Where marks are lost
Saying carbon monoxide causes acid rain or global warming. Its problem is that it is toxic.
Saying carbon dioxide causes acid rain. Acid rain is caused by sulfur dioxide and oxides of nitrogen.
Confusing global dimming (particulates reflect sunlight) with global warming (greenhouse gases absorb long wavelength radiation).
Writing vague effects such as 'harms the environment'. Name what is damaged: buildings, trees, lakes, fish.
Saying you can smell carbon monoxide. It is odourless.
Exam technique
Link each pollutant to its specific problem: 'causes pollution' does not score.
For carbon monoxide, 'toxic' is one mark and 'colourless and odourless, so not easily detected' is another.
In 6-mark pollutant answers, organise by pollutant: how it forms, then the problems it causes.
Show your working for percentage change: change ÷ original × 100.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) Which pollutant causes global dimming? Tick (✓) one box.[1]
Carbon monoxide
Particulates
Sulfur dioxide
Water vapour
(b) Why is carbon monoxide difficult to detect?[1]
(c) Name two pollutants that cause acid rain.[2]
Show the answer and mark scheme
(a)Answer: Particulates
(b)
it is colourless and odourless
(c)
sulfur dioxide
oxides of nitrogen / nitrogen dioxide
Question 2Medium5 marks
People are advised to fit carbon monoxide detectors in homes that have gas boilers.
(a) Explain why carbon monoxide is dangerous.[2]
(b) Suggest how a faulty gas boiler could produce carbon monoxide.[1]
(c) Particulates are another pollutant from burning fuels. Describe the problems caused by particulates.[2]
Show the answer and mark scheme
(a)
it is toxic / poisonous
it is colourless and odourless so it is not easily detected
(b)
not enough air / oxygen reaches the flame so the gas undergoes incomplete combustion
(c)
global dimming (they reflect sunlight, so less reaches the Earth's surface)
health problems for humans (e.g. damage to the lungs when breathed in)
Question 3Hard6 marks
The exhaust gases from diesel engines contain carbon monoxide, oxides of nitrogen, sulfur dioxide and particulates.
Explain how each of these pollutants is produced in a diesel engine, and describe the problems each pollutant causes.[6]
Show the answer and mark scheme
carbon monoxide is produced by incomplete combustion (limited oxygen)
carbon monoxide is toxic, and colourless and odourless so it is not easily detected
oxides of nitrogen form when nitrogen and oxygen from the air react at the high temperature in the engine
sulfur dioxide forms when sulfur impurities in the fuel react with oxygen
sulfur dioxide and oxides of nitrogen cause respiratory problems and acid rain
acid rain damages buildings, trees and plants, and harms aquatic life in lakes
particulates (soot and unburned hydrocarbons) are produced by incomplete combustion
particulates cause global dimming and health problems such as lung damage
Marked with levels of response: the full level descriptors are in the app.