Four samples of pond water are placed in separate transparent sealed chambers. The chambers are kept in light for 24 hours. The table gives the percentages by volume of carbon dioxide and oxygen in the air in each chamber before and after the 24 hours.
| Chamber | Initial carbon dioxide (%) | Final carbon dioxide (%) | Initial oxygen (%) | Final oxygen (%) |
|---|---|---|---|---|
| 1 | 0.10 | 0.22 | 20.20 | 20.08 |
| 2 | 0.18 | 0.06 | 20.00 | 20.00 |
| 3 | 0.20 | 0.08 | 19.80 | 19.92 |
| 4 | 0.16 | 0.10 | 20.10 | 19.98 |
Use the table. Which chamber shows the gas changes expected when photosynthesis is the main process?
Chamber 2
Chamber 1
Chamber 4
Chamber 3
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.