Chemistry of the Atmosphere - AQA GCSE Chemistry Revision

Topic overview

What you need to know

Chemistry of the Atmosphere is a key part of GCSE Chemistry. Link particles, structure and energy changes to the observations and calculations you may be given. Approximately 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and small amounts of other gases (mainly argon ~0.9%). Greenhouse gases (CO₂, methane, water vapour) absorb and re-emit infrared radiation, keeping Earth warm enough to support life. The increase in Earth's average temperature due to increased levels of greenhouse gases from human activities.

Exam tip

Balance equations, show units in calculations and connect macroscopic observations to particles.

Revision notes

Core ideas

Secure these ideas first. Say each definition in your own words, then connect it to the topic overview.

Current Atmosphere Composition: Approximately 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and small amounts of other gases (mainly argon ~0.9%).
Greenhouse Effect: Greenhouse gases (CO₂, methane, water vapour) absorb and re-emit infrared radiation, keeping Earth warm enough to support life.
Global Warming: The increase in Earth's average temperature due to increased levels of greenhouse gases from human activities.
Carbon Dioxide Increase: CO₂ levels are rising due to burning fossil fuels and deforestation. This enhances the greenhouse effect.

Revision notes

Apply it in the exam

The exam will rarely ask for an isolated definition. Practise selecting the right idea and using it as part of a complete explanation or method.

Climate Change: Long-term changes in global weather patterns caused by global warming: rising sea levels, extreme weather, ice cap melting.
Carbon Footprint: The total amount of greenhouse gases released over the full life cycle of a product, service, or event.
Early Atmosphere: Earth's early atmosphere was mainly CO₂ with little or no oxygen, similar to Mars and Venus today. Volcanic activity released gases.
How Oxygen Increased: Photosynthetic organisms (cyanobacteria and plants) produced oxygen over billions of years, gradually increasing it to ~21%.

Core knowledge

Key facts for Chemistry of the Atmosphere

8 essentials

Current Atmosphere Composition

Approximately 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, and small amounts of other gases (mainly argon ~0.9%).

Greenhouse Effect

Greenhouse gases (CO₂, methane, water vapour) absorb and re-emit infrared radiation, keeping Earth warm enough to support life.

Global Warming

The increase in Earth's average temperature due to increased levels of greenhouse gases from human activities.

Carbon Dioxide Increase

CO₂ levels are rising due to burning fossil fuels and deforestation. This enhances the greenhouse effect.

Climate Change

Long-term changes in global weather patterns caused by global warming: rising sea levels, extreme weather, ice cap melting.

Carbon Footprint

The total amount of greenhouse gases released over the full life cycle of a product, service, or event.

Early Atmosphere

Earth's early atmosphere was mainly CO₂ with little or no oxygen, similar to Mars and Venus today. Volcanic activity released gases.

How Oxygen Increased

Photosynthetic organisms (cyanobacteria and plants) produced oxygen over billions of years, gradually increasing it to ~21%.

Active recall

Close the notes and answer these

1.Without looking, explain current atmosphere composition and give one example or consequence.
2.Without looking, explain greenhouse effect and give one example or consequence.
3.Without looking, explain global warming and give one example or consequence.
4.Without looking, explain carbon dioxide increase and give one example or consequence.

Content reviewed 23 July 2026 against the current linked specification.

Finished learning?

Mark the notes complete, then test what you can recall.

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