1. 4.7 (a) To investigate the influence of light intensity on the rate of photosynthesis

2. Step 1 Cut the stem of the elodea at an angle. Remove several leaves from the cut end of the stem.

3. Before you start get or make a copy of this Table of results Distance [d] from light source (cm) Light Intensity or 1 / d 2 (No. of bubbles/ minute) Average Trial 1Trial 2Trial 3

4. Step 2 Hook a paper clip onto the end of the elodea. Drop the elodea, stem up, into a boiling tube of pond water.

5. Step 3 Place the boiling tube, containing the elodea into a water bath at 25°C.

6. Step 4 Switch on the light source and place the water bath containing the elodea 15 cm from the lamp. Wait 5 minutes.

7. Step 5 Observe bubbles being released from the cut end of the stem. Count and record the number of bubbles released per minute. Repeat twice.

8. Step 6 Repeat the experiment, varying the distance between the water bath and the lamp.

9. Table of results: Distance from light source (cm) Light Intensity or 1 / d 2 (No. of bubbles/ minute) Average Trial 1Trial 2Trial 3

10. Step 7 Plot a graph of light intensity against average no. of bubbles/minute.

11. Expected Graph

12. END