Practicals

• What is the process of photosynthesis in green plants?

  Green plants use carbon dioxide and water in the presence of light energy to produce glucose and oxygen.
• What factors can affect the rate of photosynthesis in plants?

  • Light intensity
  • Carbon dioxide concentration
  • Temperature
• How can light intensity be changed in a photosynthesis experiment?

  By changing the distance between the pond weed and the light source.
• What type of plant is used in the photosynthesis practical described?

  Aquatic plant, specifically common pond weed.
• Why is sodium hydrogen carbonate solution added to the boiling tube in the experiment?

  It encourages the pond weed to photosynthesize.
• What is the purpose of cutting the stem of the pond weed underwater?

  To ensure a steady stream of oxygen bubbles is produced.
• How is the rate of photosynthesis measured in this experiment?

  By counting the number of bubbles of oxygen gas produced in one minute.
• Why is it important to cut the pond weed at an angle?

  It ensures a nice steady stream of oxygen bubbles comes from it.
• What is the independent variable in the photosynthesis experiment?

  The light intensity.
• What should be done to ensure a fair test when measuring the rate of photosynthesis?

  Only one variable should be changed at a time, such as light intensity.
• What distance was initially set between the light source and the pond weed?

  10 centimeters.
• What happens to the number of bubbles produced as the distance from the light source increases?

  The number of bubbles produced decreases.
• What is an alternative method to measure the rate of photosynthesis?

  • Collect the volume of oxygen produced.
  • Use a glass funnel to trap the pond weed.
  • Invert a boiling tube over the funnel to collect oxygen.
• How can the collected oxygen be tested to confirm it is oxygen gas?

  By using a glowing splint, which should relight in the presence of oxygen.
• What is the purpose of using a boiling tube in the experiment?

  To collect and measure the volume of oxygen produced.