A scientist investigates changes in the gases above water in a sealed container. Gas volumes are measured at the same temperature and pressure.
| Stage | Treatment | Volume of nitrogen in cm3\text{cm}^3cm3 | Volume of carbon dioxide in cm3\text{cm}^3cm3 | Volume of oxygen in cm3\text{cm}^3cm3 |
|---|---|---|---|---|
| 1 | Before the gases contact the water | 20 | 80 | 0 |
| 2 | After the gases have been mixed with the water | 20 | 10 | 0 |
| 3 | After algae have grown in the light | 20 | 2 | 8 |
Use the data to explain how and why the percentage by volume of nitrogen changes from stage 1 to stage 3.
A scientist says that this investigation proves that the Earth's atmosphere changed in exactly the same way. Explain why this statement is not justified.
79 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.