Scientists use the gases released by volcanoes today as evidence for the composition of the Earth's early atmosphere. The table shows the composition of the gas released by one volcano.
| Gas | Percentage (%) by volume |
|---|---|
| water vapour | 70 |
| carbon dioxide | 15 |
| sulfur dioxide | 8 |
| nitrogen | 5 |
| other gases | 2 |
Use the table to give the two gases that are likely to have made up most of the Earth's early atmosphere.
Explain why the Earth's early atmosphere contained little or no oxygen. Use the table in your answer.
The atmospheres of Mars and Venus today are about 95 % carbon dioxide. There is no life on Mars or Venus.
Explain how this information supports the theory that the Earth's early atmosphere was mainly carbon dioxide.
Explain why scientists cannot be certain about the composition of the Earth's early atmosphere.
Nitrogen is only 5 % of the volcanic gas but is 78 % of the atmosphere today. Suggest why nitrogen built up in the atmosphere over time.
97 exam-style questions on Edexcel GCSE Chemistry 9.2 Earth and atmospheric science, covering 9.2.1 The Earth's early atmosphere, 9.2.2 How the atmosphere evolved, 9.2.3 Chemical test for oxygen, and 9.2.4 The greenhouse effect and climate change. Each one has a worked solution and a mark scheme showing where the marks go.