Scientists think that the Earth's atmosphere has changed over billions of years.
Explain how the oceans formed.
Describe how the formation of the oceans caused the percentage of carbon dioxide in the atmosphere to decrease.
The table shows estimates of the percentage of oxygen in the atmosphere at different times.
| Time / billion years ago | Oxygen / % |
|---|---|
| 3.0 | 0 |
| 2.0 | 1 |
| 1.0 | 2 |
| 0.5 | 10 |
| 0 (today) | 21 |
Describe how the percentage of oxygen in the atmosphere changed over the last 3 billion years. Use data from the table in your answer.
Explain why the percentage of oxygen in the atmosphere increased.
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.