GCSE Biology Required Practical: Factors Affecting the Rate of Photosynthesis

Key Stage 4

Meaning

Investigate the effects of light intensity on the rate of photosynthesis.

Method

• Independent Variable - Distance between the light source and plant.
• Dependent Variable - Number of bubbles produced by the plant.
• Control Variables - Brightness of the light. Frequencies that the light emits. Ensure no other light source than the one used in the experiment.

1. Fill a boiling tube with 0.2% solution of sodium hydrogen carbonate.
2. Place a length of pond weed in the boiling tube with the cut end at the top.
3. Use a metre rule with zero at the light source to fix the boiling tube at 10cm from the light source.
4. Use a timer to count the number of bubbles produced by the pond weed.
5. Repeat steps three and four 6 times increasing the distance by 10cm each time.