Spec 8462
Revise AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere with the question bank and revision guides.
For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today: • about four-fifths (approximately 80%) nitrogen • about one-fifth (approximately 20%) oxygen • small proportions of various other gases, including carbon dioxide, water vapour and noble gases.
