photosynthesis

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

  How to investigate the effect of light intensity on the rate of photosynthesis
• What additional concept should higher tier students be able to explain?

  How the results are affected by the inverse square law
• What is the first step in the practical investigation of photosynthesis?

  • Take a boiling tube
  • Place it 10 centimeters away from an LED light source
• Why is an LED light used in the experiment?

  Because it doesn't release much heat, which could change the temperature of the experiment
• What should you do if using a normal light bulb instead of an LED light?

  Place a beaker of water between the light and the boiling tube
• What solution is filled in the boiling tube for the experiment?

  Sodium hydrogen carbonate solution
• What does sodium hydrogen carbonate solution release that is needed for photosynthesis?

  Carbon dioxide
• What should be placed in the boiling tube along with the sodium hydrogen carbonate solution?

  A piece of pond weed
• How long should the pond weed be left to acclimatize to the conditions?

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

  Oxygen
• How do you measure the rate of photosynthesis in this experiment?

  By counting the number of bubbles produced in one minute
• What should you do after counting the bubbles for one minute?

  Repeat the counting two more times and calculate the mean
• What distances should the experiment be repeated at after the initial 10 centimeters?

  20 centimeters, 30 centimeters, and 40 centimeters
• What are the two main problems with counting bubbles in this practical?

  1. The number of bubbles can be too fast to count accurately
  2. Bubbles are not always the same size
• How can the problems with counting bubbles be solved?

  By measuring the volume of oxygen produced instead of counting bubbles
• What equipment is used to measure the volume of oxygen produced?

  A measuring cylinder filled with water
• What happens to the number of bubbles per minute when the distance from the light source is doubled?

  The number of bubbles falls by a factor of four
• What scientific principle explains the decrease in bubbles when the distance is doubled?

  The inverse square law
• Why does the light intensity fall by four times when the distance is doubled?

  Because light spreads out as it travels, reducing intensity
• What should students remember about the required practical?

  • Plenty of questions will be found in the vision workbook
  • Students can access it via a provided link
• What should students be able to describe after watching the video?

  How to investigate the effect of light intensity on the rate of photosynthesis
• What is the relationship between light intensity and the rate of photosynthesis?

  Higher light intensity increases the rate of photosynthesis
• How does the inverse square law relate to light intensity and distance?

  As distance increases, light intensity decreases by the square of the distance