photosynthesis

• What should you be able to describe by the end of the video?

  Investigate the effect of light intensity
• What is the significance of the inverse square law in this experiment?

  It explains how light intensity affects photosynthesis
• What equipment is used to start the experiment?

  • Boiling tube
  • LED light source
  • Sodium hydrogen carbonate solution
  • Pond weed
• Why is an LED light source preferred over a normal light bulb?

  It releases less heat, maintaining temperature
• What role does sodium hydrogen carbonate solution play in the experiment?

  It releases carbon dioxide needed for 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
• How do you measure the rate of photosynthesis in this experiment?

  Count the number of bubbles produced
• What is a problem with counting bubbles in the experiment?

  The bubbles can be too fast to count accurately
• How can the problem of bubble size be solved?

  By measuring the volume of oxygen produced
• What is the procedure for measuring the volume of oxygen produced?

  1. Place pond weed in a formal
  2. Catch bubbles in a measuring cylinder
  3. Measure the volume of oxygen produced
• What happens to the number of bubbles per minute as the distance from the light source increases?

  It falls by a factor of four
• What does doubling the distance from the light source do to light intensity?

  It falls by a factor of four
• Why does the number of oxygen bubbles fall as light intensity decreases?

  Less light is available for photosynthesis
• What is the relationship between distance and the number of bubbles produced?

  • Doubling distance reduces bubbles by a factor of four
  • Example: 10 cm to 20 cm reduces bubbles by 4 times
• Where can you find more questions on this required practical?

  In the vision workbook
• What should higher tier students be able to explain regarding the experiment?

  How results are affected by the inverse square law