A student measured the percentage of oxygen in the air inside two sealed containers. One container held algae in water and the other held only water. Both containers were kept in the light.
| Container | Oxygen at the start | Oxygen after 24 hours |
|---|---|---|
| With algae | 20.0% | 21.6% |
| Without algae | 20.0% | 20.0% |
Explain what the results show about how oxygen can be added to the atmosphere.
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.