pratical 5

• Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler.
• Fill the boiling tube with a fixed volume of 0.2% sodium hydrogen carbonate solution.
• Place the cut pondweed into the boiling tube with the cut end at the top.
• Gently push the pondweed down with the glass rod.
• Leave the boiling tube to rest for 5 minutes.
• Start the stopwatch and count the number of bubbles produced in one minute.
• For each light intensity/distance, repeat the count twice more and take a mean.
• Record in a table as seen below.
• Repeat steps 1-7 for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source.
• Plot a graph of the rate of photosynthesis (given by the number of bubbles) against light intensity (using the inverse square law, light intensity ∝ 1/distance2 between pondweed and light source).
• Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler.
• Fill the boiling tube with a fixed volume of 0.2% sodium hydrogen carbonate solution.
• Place the cut pondweed into the boiling tube with the cut end at the top.
• Gently push the pondweed down with the glass rod.
• Leave the boiling tube to rest for 5 minutes.
• Start the stopwatch and count the number of bubbles produced in one minute.
• For each sodium hydrogen carbonate concentration, repeat the count twice more and take a mean.
• Record in a table as seen below.
• Repeat steps 1-7 for 3 more concentrations of sodium hydrogen carbonate solution.
• Plot a graph of the rate of photosynthesis (given by the number of bubbles) against sodium hydrogen carbonate concentration.
• chlorophyll

  1. Use a variegated leaf (with green parts and white parts).
  2. Immerse the leaf in boiling water for 30 seconds.
  3. Carefully spread onto a white tile so the colour change can be accurately seen.
  4. Use a dropping pipette to add iodine solution to the leaf.
  5. The green parts of the leaf should turn blue-black due to the presence of starch the whiteareas should not.