AQA GCSE Combined Science Foundation (8464), Foundation tier · Chemistry › Chemistry of the atmosphere › Carbon dioxide and methane as greenhouse gases
Practise The carbon footprint and its reduction. 7 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What a carbon footprint is, how it can be reduced by cutting emissions of carbon dioxide and methane, and why these actions may be limited. Expect a definition, 'describe actions' and 'give reasons why actions may be limited' questions, and data questions that compare emissions.
Key facts
Carbon footprint = total CO2 and other greenhouse gases emitted over the full life cycle of a product, service or event
Full life cycle: raw materials → manufacture → transport → use → disposal
Reduce a footprint by cutting emissions of carbon dioxide and methane
Actions: alternative energy, energy conservation, carbon capture and storage, carbon taxes and licences, carbon off-setting (e.g. tree planting), carbon neutrality
Carbon neutral = zero net release of carbon dioxide
Limits: scientific disagreement, lack of public information and education, lifestyle changes, economic considerations, incomplete international cooperation
1 kg = 1000 g and 1 tonne = 1000 kg
Notes
What a carbon footprint is
diagram
The carbon footprint is the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
Full life cycle means every stage: getting the raw materials, manufacturing, transport, use and disposal.
The footprint counts the whole life cycle, not just the use.
A carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.
Actions to reduce emissions
Alternative energy supplies: more use of renewable resources (such as wind, solar and hydroelectric power) and nuclear power instead of fossil fuels.
Energy conservation: using less energy, e.g. insulating buildings, using efficient appliances, and using public transport.
Carbon capture and storage: carbon dioxide from power stations or factories is captured and stored deep underground, e.g. in old oil and gas fields, instead of being released.
Carbon taxes and licences: making companies pay for the greenhouse gases they release, or allowing them to release only a limited amount, encourages them to emit less.
Carbon off-setting: balancing emissions by paying for actions that remove carbon dioxide, such as planting trees, which absorb carbon dioxide by photosynthesis.
Carbon neutrality: activities with zero net release of carbon dioxide, because any carbon dioxide released is balanced by the same amount removed or offset.
Reducing methane: collect methane from landfill sites and burn it as a fuel, send less waste to landfill, and farm fewer livestock (e.g. by people eating less meat).
Why actions may be limited
Scientific disagreement over the causes and consequences of global climate change.
Lack of public information and education, so people don't know what to do or why.
People may not want to make lifestyle changes, e.g. flying less or changing their diet.
Economic considerations: many actions are expensive, and some countries depend on fossil fuels for jobs, income and development.
Incomplete international cooperation: not every country agrees to cut emissions, and one country acting alone has a limited effect.
How to answer each type of question
Define carbon footprint
2 marksGrade 4
Say it is the TOTAL amount of carbon dioxide and other greenhouse gases.
Say it is over the FULL LIFE CYCLE of a product, service or event.
Example. What is meant by the carbon footprint of a product?
Show the model answerHide the model answer
The total amount of carbon dioxide and other greenhouse gases emitted (1) over the full life cycle of the product (1).
Describe actions to reduce emissions
2 to 3 marksGrade 5
Give different actions, not the same idea twice.
For each one, say how it reduces emissions (e.g. 'so less fossil fuel is burned').
Example. A school wants to reduce the carbon footprint of its buildings. Describe three actions it could take.
Show the model answerHide the model answer
Any three from: fit solar panels, or buy electricity from renewable sources, so less fossil fuel is burned (1) insulate the buildings or use energy-efficient lighting, to conserve energy (1) plant trees to offset some of its carbon dioxide emissions (1) send less waste to landfill, e.g. by recycling or composting, to reduce methane emissions (1)
Don’t lose marks
Defining carbon footprint as 'the carbon dioxide from burning fuel'. It includes other greenhouse gases and the whole life cycle.
Writing 'be more eco-friendly' or 'recycle' without saying how it reduces emissions.
Thinking that planting trees cancels emissions straight away. Trees take years to absorb the carbon dioxide.
Saying carbon neutral means 'releases no carbon dioxide'. It means zero NET release.
Giving more actions when the question asks why actions may be limited.
More tips
Memory tricks
Carbon footprint = 'cradle to grave': count every stage, from raw materials to disposal.
Six actions: 'All Countries Could Try Offsetting Now': Alternative energy, Conservation, Capture and storage, Taxes and licences, Off-setting, Neutrality.
Five limits: 'Some People Like Eating Ice cream': Scientific disagreement, Public information lacking, Lifestyle changes, Economic considerations, International cooperation incomplete.
Unit check: g → kg ÷ 1000, kg → tonnes ÷ 1000.
Exam technique
A definition of carbon footprint needs three ideas: total, carbon dioxide and other greenhouse gases, full life cycle.
'Give reasons why actions may be limited' wants barriers such as cost, cooperation, lifestyle, information and disagreement.
In 'evaluate' questions, use data from the question, compare the options and finish with a justified judgement.
Show each step of a calculation with its unit.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
Give one way to reduce carbon dioxide emissionsFor example, generate electricity from renewable resources instead of burning fossil fuels.
Grade 4
Define carbon footprintThe total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.
Grade 5
Describe actions to reduce emissionsAlternative energy, energy conservation, carbon capture and storage, carbon taxes and licences, carbon off-setting and carbon neutrality.
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) What is meant by the carbon footprint of a product?[1]
(b) Give two ways of reducing emissions of carbon dioxide.[2]
(c) Which action would reduce emissions of methane? Tick (✓) one box.[1]
Building more landfill sites
Driving electric cars
Eating less meat from cattle
Using more fertiliser
Show the answer and mark scheme
(a)
the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of the product
(b)
use alternative energy sources (e.g. wind, solar, nuclear)
energy conservation (e.g. insulating homes)
carbon capture and storage
carbon taxes / licences
carbon off-setting (e.g. planting trees)
(c)Answer: Eating less meat from cattle
Question 2Medium6 marks
A government plans to reduce its country’s carbon footprint by building wind farms and introducing a carbon tax.
(a) Explain how a carbon tax could reduce emissions of carbon dioxide.[2]
(b) Explain how building wind farms could reduce the country’s carbon footprint.[1]
(c) Give three reasons why actions to reduce a country’s carbon footprint may be limited.[3]
Show the answer and mark scheme
(a)
companies / people pay tax for the carbon dioxide they emit (or for fossil fuels they use)
so they are encouraged to use less fossil fuel / switch to low-carbon energy sources
(b)
electricity is generated without burning fossil fuels, so less carbon dioxide is emitted
(c)
scientific disagreement over the causes and consequences of global climate change
lack of public information and education
people are unwilling to change their lifestyles
economic considerations / cost (e.g. of new technology, effects on jobs)
incomplete international cooperation (other countries may not reduce their emissions)