Photosynthesis

• Method

  1. Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler

  2. Fill the boiling tube with a fixed volume of sodium hydrogen carbonate solution

  3. Place the cut pondweed into the boiling tube with the cut end at the top. Gently push the pondweed down with the glass rod

  4. Leave the boiling tube to rest for 5 minutes

  5. Start the stopwatch and count the number of bubbles produced in one minute

  6. For each light intensity/distance, repeat the count twice more and take a mean

  7. Record in a table as seen below

  8. Repeat steps 1-7 for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source

  9. Plot a graph of the rate of photosynthesis (given by the no. of bubbles) against light intensity (using the inverse square law, light intensity = 1/distance? between pondweed and light source)
• The test tube rack containing a boiling tube is placed 10 cm away from the light source, measured using the ruler
• The boiling tube is filled with a fixed volume of sodium hydrogen carbonate solution
• The cut pondweed is placed into the boiling tube with the cut end at the top, and gently pushed down with the glass rod
• The boiling tube is left to rest for 5 minutes
• The number of bubbles produced in one minute is counted, and the count is repeated twice more for each light intensity/distance, with a mean taken
• The results are recorded in a table
• The process is repeated for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source
• A graph is plotted of the rate of photosynthesis (given by the no. of bubbles) against light intensity (using the inverse square law, light intensity = 1/distance? between pondweed and light source)