GCSE Chemistry · AQA 8462 · Topic 4.9
Chemistry of the atmosphere
Key points
- For about the last 200 million years the atmosphere has been roughly 80% nitrogen, 20% oxygen and small amounts of other gases such as carbon dioxide, water vapour and noble gases.
- The early atmosphere probably came from volcanoes and was mainly carbon dioxide; oceans formed as water vapour condensed.
- Oxygen increased when algae and plants began photosynthesis; carbon dioxide decreased through photosynthesis and by forming sedimentary rocks and fossil fuels.
- Greenhouse gases (carbon dioxide, methane, water vapour) keep the Earth warm. Human activities increase them, leading to global climate change.
- The carbon footprint is the total greenhouse gas emitted over a product's life cycle.
- Burning fuels releases pollutants: carbon monoxide, sulfur dioxide, oxides of nitrogen and particulates.
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The air around us has not always been the same. This topic tells the story of how the Earth's atmosphere formed and changed, and then looks at how human activity is changing it now, through greenhouse gases and pollutants.
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