CP 6: Photosynthesis

• What is produced during photosynthesis?

  Oxygen
• What methods can be used to measure the rate of photosynthesis in a plant?

  • Count the number of bubbles produced
  • Collect bubbles in a syringe over a set time (e.g., one minute)

  
• How does light intensity influence photosynthesis?

  It affects the rate of photosynthesis

  
• Where can you find an online virtual experiment related to photosynthesis?

  At the University of Reading's website
• What is the aim of the photosynthesis investigation described?

  To investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism
• How is the rate of photosynthesis measured in this experiment?

  By observing the degree of colour change in the bicarbonate indicator solution
• What does the bicarbonate indicator solution change colour with?

  Increasing concentrations of CO​2​
• What equipment is needed for the photosynthesis experiment?

  • Boiling tube
  • Algal beads
  • Light source
  • Ruler
  • Test tube rack
  • Stopwatch
  • Glass rod
  • Measuring cylinder
  • Bicarbonate indicator solution
  • Bicarbonate indicator colour standard chart
• What is the first step in the method of the experiment?

  Place a test tube rack containing a boiling tube 10 cm away from the light source
• How far should the boiling tube be placed from the light source?

  10 cm
• What should be done after placing the algal beads into the boiling tube?

  Fill the boiling tube with a fixed volume of bicarbonate indicator
• What should be recorded after filling the boiling tube with bicarbonate indicator?

  The initial colour and pH of the solution
• How long should the solution be observed before recording the final colour and pH?

  30 minutes
• What should be done after recording the final colour and pH?

  Repeat the steps for 3 more distances from the light source
• What is the relationship between light intensity and distance in this experiment?

  Light intensity is given by the inverse square law, $\text{light intensity} =$$\frac{1}{\text{distance}^2}$
• What controlled variables are mentioned in the experiment?

  • Temperature (can use a water bath)
  • Amount of carbon dioxide available at the start
  • Volume of indicator solution
• Why might temperature be a factor affecting the rate of photosynthesis?

  Because temperature can influence the metabolic rate of the organism
• What is a potential source of error in judging the colour of the solution?

  The colour may be difficult to judge and match to the colour standard chart
• What are the potential hazards mentioned in the experiment?

  • Be careful with boiling water
  • Potential allergy risk from the algae
  • Lamp may get hot
  • Keep water away from electrical power outlets and wiring