A student investigated the effect of light intensity on the rate of photosynthesis in pondweed. The student used a filament lamp and did not use a heat shield.
The student also measured the temperature of the water around the pondweed at the end of each test.
The Table shows the results.
Table
| Distance from lamp in cm\text{cm}cm | Volume of gas collected in 5 minutes in cm3\text{cm}^3cm3 | Temperature of water at the end of the test in ∘C^{\circ}\text{C}∘C |
|---|---|---|
| 40 | 0.6 | 20 |
| 30 | 1.1 | 20 |
| 20 | 2.4 | 21 |
| 10 | 6.1 | 27 |
| 5 | 3.0 | 45 |
Calculate the rate of gas production at 20 cm in cm3\text{cm}^3cm3 per minute.
Show that the results at 40 cm and 20 cm support the inverse square law.
Explain why the volume of gas collected at 5 cm is lower than the volume collected at 10 cm.
Suggest two improvements to the method that would make the results more valid.
44 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.