Photosynthesis

• 1. Start with a boiling tube and place it 10cm away from the LED light source
• An LED light is used as these do not release very much heat
• 2. Fill the boiling tube with sodium hydrogen carbonate solution. Sodium hydrogen carbonate solution releases carbon dioxide, which is needed for photosynthesis
• 3. Put a piece of pondweed into the boiling tube with the cut end at the top
• 4. Leave this for 5 minutes to acclimatise to the conditions in the boiling tube
• 5. Bubbles of gas will produce from the cut end of the pondweed. This gas is oxygen and that is produced by photosynthesis
• 6. Start a stopwatch and count the number of bubbles that are produced in 1 minute
• 7. Repeat this two more times and calculate the mean of bubbles produced in 1 minute
• 8. Do the experiment again from the start at 20cm, then 30cm, then 40cm
• The number of bubbles can be too fast to count accurately
• 9. Place the pondweed under a funnel and catch the bubbles in a measuring cylinder
• 10. Use the measuring cylinder to measure the volume of the oxygen gas produced