Required Practical: Photosynthesis

• What type of light source is used in the experiment?

  LED light source
• Why is an LED light preferred for this experiment?

  It doesn't release much heat
• What should be placed between a normal light bulb and the boiling tube?

  A beaker of water
• What does sodium hydrogen carbonate solution release?

  Carbon dioxide
• What is the purpose of adding pond weed to the boiling tube?

  To produce oxygen through photosynthesis
• How long should the pond weed acclimatize in the boiling tube?

  Five minutes
• What gas is produced by the pond weed during photosynthesis?

  Oxygen
• What should you do after starting the stopwatch?

  Count the number of bubbles produced
• How many times should the bubble count be repeated?

  Two more times
• What is a problem with counting bubbles?

  They can be too fast to count accurately
• Why is measuring bubble size a problem?

  Bubbles are not always the same size
• How can the problem of counting bubbles be solved?

  Measure the volume of oxygen produced
• What happens when you plot the mean number of bubbles against distance?

  You get a graph showing the relationship
• What equipment is used to measure the volume of oxygen?

  A measuring cylinder
• What happens to the number of bubbles when the distance is doubled?

  It falls by a factor of four
• What is the inverse square law related to in this experiment?

  Light intensity and distance from the light
• Why does light intensity affect the number of oxygen bubbles?

  Photosynthesis requires light for oxygen production
• What are the steps to investigate the effect of light intensity on photosynthesis?

  1. Set up boiling tube with sodium hydrogen carbonate solution.
  2. Place pond weed in the boiling tube.
  3. Position light source at specified distances (10 cm, 20 cm, 30 cm, 40 cm).
  4. Count bubbles produced or measure oxygen volume.
  5. Repeat and calculate mean results.
• What is the relationship between distance and light intensity in photosynthesis?

  • Doubling the distance reduces light intensity by a factor of four.
  • This results in a corresponding decrease in oxygen production.