Volcanoes released nitrogen into the Earth's early atmosphere. Today about 80% of the Earth's atmosphere is nitrogen.
Explain why the percentage of nitrogen in the atmosphere increased during the first two billion years of the Earth's existence.
A student says that algae must have produced the nitrogen, because the percentage of nitrogen increased at the same time as the percentage of oxygen. Explain why the student is not correct.
40 exam-style questions on AQA GCSE Chemistry 9.1 The composition and evolution of the Earth's atmosphere, covering 9.1.1 The proportions of different gases in the atmosphere, 9.1.2 The Earth's early atmosphere, 9.1.3 How oxygen increased, and 9.1.4 How carbon dioxide decreased. Each one has a worked solution and a mark scheme showing where the marks go.