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• INVESTIGATING PHOTOSYNTHESIS

  • The effect of light intensity on photosynthesis can be investigated in water plants.
  • The plants will release bubbles of oxygen - a product of photosynthesis
• INVESTIAGTING PHOTOSYNTHESIS:

  • A lamp with an LED bulb (doesn't raise water temperature) is set up at different distances from the plant in a beaker of water:
  • sodium hydrogen-carbonate - formula NaHCO3 - is added to the water to supply carbon dioxide - a reactant in photosynthesis - to the plant
  • the light intensity is related to distance - it will decrease as the distance away from the bulb increases - so light intensity for the investigation can be varied by changing the distance from the lamp to the plant.
  • The bubbles produced over one minute periods are recorded.
• INVESTIAGTING PHOTOSYNTHESIS:

  Aim

  To investigate the effect of light intensity on the rate of photosynthesis.
• INVESTIGATING PHOTOSYNTHESIS:

  Method

  1. Set up a boiling tube containing 45 cm³ of sodium hydrogen-carbonate solution (1%).
  2. Cut a piece of the pondweed to 8 cm long.
  3. Place the pondweed in the boiling tube carefully. The pondweed should be cut end uppermost.
  4. Position the boiling tube so that the pondweed is 10 cm away from the light source. Count the number of bubbles emerging in one minute. Repeat five times and record results.
  5. Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
• INVESTIGATING PHOTOSYNTHESIS:

  Variables

  • Independent variable - distance from the light source/light intensity.
  • Dependent variable - the number of bubbles produced per minute.
  • Control variables - concentration of sodium hydrogencarbonate solution, temperature, using the same piece of Cabomba pondweed each time.
• INVESTIGATING PHOTOSYNTHESIS:

  Risks

  Care must be taken when using water near electrical equipment. Ensure that your hands are dry when handling the lamp.