Some students investigate the rate of decomposition of domestic green waste. They set up four compost bins with different numbers of ventilation holes to control the air supply.
They measure the total mass of each bin and its contents at the start and after a period of 6 weeks. The table below shows their results:
| Number of ventilation holes | Mass of bin and waste at the start (g) | Mass of bin and waste after 6 weeks (g) |
|---|---|---|
| 4 | 400 | 360 |
| 8 | 400 | 334 |
| 16 | 400 | 322 |
| 32 | 400 | 312 |
Determine the following:
Identify the independent variable in this investigation.
Calculate the average loss in mass per week of the bin and waste with 32 ventilation holes. Give your answer to 3 significant figures.
44 exam-style questions on OCR GCSE Biology Practical skills. Each one has a worked solution and a mark scheme showing where the marks go.