Required Practical 6: Photosynthesis

1. Take a boiling tube and place it 10cm away from an LED light source.

If you use a light bulb, you have to place a beaker of water between the light and boiling tube

2. Fill the tube with sodium hydrogen carbonate solution

3. Put a piece of pondweed into the boiling tube with the cut end at the top

4. Leave for 5 minutes

5. Count the amount of bubbles produced in 1 minute

The bubbles of gas you see is oxygen

6. Repeat 2 times and find the mean

7. Move the tube at 10cm intervals and repeat the steps 5 and 6

TO GET MORE ACCURATE RESULTS

1. Place the pondweed under a funnel and catch the bubbles in a measuring cylinder

2. Use the measuring cylinder to measure the volume of gas produced

If we double the distance, then the number of bubbles per minute fall by a factor of four, which is called the inverse square law