A student places three transparent chambers in sunlight. Air at the same temperature is passed through each chamber at the same rate.
| Chamber | Contents | Water vapour concentration entering chamber / g m−3\text{g m}^{-3}g m−3 | Water vapour concentration leaving chamber / g m−3\text{g m}^{-3}g m−3 |
|---|---|---|---|
| A | moist soil with no plant | 7.2 | 8.4 |
| B | moist soil covered by a waterproof sheet, with no plant | 7.2 | 7.2 |
| C | a leafy plant rooted in moist soil covered by a waterproof sheet | 7.2 | 10.6 |
Equal volumes of air leaving the chambers are collected and cooled to the same lower temperature.
Explain why the results from chambers A and B show that the waterproof sheet is needed in chamber C.
Suggest which outlet air sample will form the greatest mass of liquid droplets when cooled. Explain both how the water vapour concentration increased in this sample and how the droplets then form. Use the results in your answer.
101 exam-style questions on Edexcel GCSE Biology 9.3 Material cycles and decomposition, covering 9.3.1 Cycling of materials through ecosystems, 9.3.2 The carbon cycle, 9.3.3 The water cycle, 9.3.4 The nitrogen cycle, 9.3.5 Indicator species and pollution, 9.3.6 Decomposition in preservation and composting, and 9.3.7 Rate changes in decay of biological material. Each one has a worked solution and a mark scheme showing where the marks go.