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This lesson covers the composition of the Earth's atmosphere, how it has changed over time, and the evidence and science behind climate change. These topics are part of the AQA GCSE Combined Science Trilogy (8464) chemistry specification.
The proportions of gases in the Earth's atmosphere have been roughly the same for the last 200 million years.
pie title Approximate Composition of the Atmosphere
"Nitrogen (N₂)" : 78
"Oxygen (O₂)" : 21
"Argon and other gases" : 1
| Gas | Approximate Percentage |
|---|---|
| Nitrogen (N₂) | 78% |
| Oxygen (O₂) | 21% |
| Argon (Ar) | 0.93% |
| Carbon dioxide (CO₂) | 0.04% |
| Water vapour | Variable (typically 1–4%) |
Exam Tip: You must know the approximate percentages: ~78% nitrogen, ~21% oxygen, ~1% other gases (mainly argon). Carbon dioxide is only about 0.04%.
The Earth's early atmosphere was very different from today. It was formed by volcanic activity and is thought to have contained:
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