Some students investigate the rate of corrosion of a steel alloy. They place four identical steel plates in beakers containing sodium chloride (NaCl) solutions of different concentrations.
They measure the mass of each steel plate at the start of the experiment and again after a period of 14 weeks. The table below shows their results:
| Concentration of NaCl solution (wt%) | Mass of steel plate at the start (g) | Mass of steel plate after 14 weeks (g) |
|---|---|---|
| 2.0 | 180.0 | 175.8 |
| 4.0 | 180.0 | 172.1 |
| 8.0 | 180.0 | 167.4 |
| 16.0 | 180.0 | 161.2 |
Determine the following:
Identify the independent variable in this investigation.
Calculate the average loss in mass per week of the steel plate in the 16.0 wt% NaCl solution. 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.