photosynthesis required practical

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

  Investigate the effect of light intensity
• What additional concept should higher tier students explain?

  How results are affected by the inverse square law
• What are the steps to investigate light intensity's effect on photosynthesis?

  1. Place a boiling tube 10 cm from an LED light.
  2. Use sodium hydrogen carbonate solution.
  3. Add pond weed and acclimatize for 5 minutes.
  4. Count bubbles of oxygen produced in one minute.
  5. Repeat at distances of 20 cm, 30 cm, and 40 cm.
• Why is an LED light used in the experiment?

  It doesn't release much heat
• What should be done if a normal light bulb is used?

  Place a beaker of water between the light and boiling tube
• What does sodium hydrogen carbonate solution release?

  Carbon dioxide
• What is observed from the cut end of the pond weed?

  Bubbles of gas being produced
• What gas is produced by photosynthesis?

  Oxygen
• How is the mean number of bubbles calculated?

  By repeating the count two more times
• What are the two main problems with counting bubbles?

  Counting can be inaccurate and bubble sizes vary
• How can the problems with counting bubbles be solved?

  Measure the volume of oxygen produced
• What equipment is used to measure the volume of oxygen produced?

  A measuring cylinder filled with water
• What is the relationship between distance and the number of bubbles produced?

  • Doubling the distance reduces bubbles by a factor of four.
  • From 10 cm to 20 cm, bubbles fall by four times.
  • From 20 cm to 40 cm, bubbles again fall by four times.
• What is the inverse square law in this context?

  Light intensity falls by a factor of four when distance doubles
• What is necessary for photosynthesis to occur?

  Light
• What happens to the number of oxygen bubbles as light intensity decreases?

  The number of bubbles produced decreases
• Where can students find more questions on this practical?

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

  How results are affected by the inverse square law
• What is the purpose of acclimatizing the pond weed?

  To adjust to the conditions in the boiling tube