Plant-fibre seedling pots are designed to decompose after use. A researcher places equal amounts of the pot material in two mesh containers at 22 °C. Both containers have the same unrestricted supply of air. Container M is kept moist and container D is kept dry.
The researcher determines the dry mass of the material at the start and after 15 days.
| Container | Initial dry mass in g | Dry mass after 15 days in g |
|---|---|---|
| M | 30.0 | 21.0 |
| D | 30.0 | 28.5 |
Calculate the difference between the mean rates of decay in containers M and D. Give your answer in g per day.
Explain why the mean rate of decay was lower in container D.
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.