Skip to content
Oak National Academy
Oak National Academy
View my library
0
Teachers
Pupils
New
New

    The effect of light intensity on rate of photosynthesis in pondweed: practical

    I can carry out an investigation into the effect of light intensity on the rate of photosynthesis in pondweed.

    Download all
    New
    New

      The effect of light intensity on rate of photosynthesis in pondweed: practical

      I can carry out an investigation into the effect of light intensity on the rate of photosynthesis in pondweed.

      Download all

      These resources will be removed by end of Summer Term 2025.

      Switch to our new teaching resources now - designed by teachers and leading subject experts, and tested in classrooms.

      These resources were created for remote use during the pandemic and are not designed for classroom teaching.

      View new resources

      Lesson details

      Key learning points

      1. Following an appropriate method to vary light intensity and measure the gas given off
      2. Accurate measurement of variables (distance, time, amount of gas) and control of variables that might affect the results
      3. Counting bubbles and measuring volume of gas given off
      4. Record results in an appropriate table

      Keywords

      • Light intensity - the amount of light reaching a given surface area in a period of time

      • Rate - a measure of how much change occurs per unit of time

      • Variable - a factor that can be changed during an experiment

      • Control variable - a factor that is kept the same during an experiment

      • Accurate - a measurement result is considered accurate if it is judged to be close to the true value

      Common misconception

      Some pupils do not consider how to control variables carefully enough. This means results are likely to be less accurate and so do not provide conclusions that can be used to support a hypothesis.

      Each type of variable is considered during the lesson and repeated to help pupils to understand the differences between each type of variable.

      Make sure the pondweed is freshly cut and that the cut is made under water; if bubbles are not produced by the pondweed, try cutting the stem again. Depending on your class, you may wish to have a discussion about why some bubble are different sizes (e.g. stomata opening in response to light).
      Teacher tip

      Equipment

      Light source, stopclock, plasticine, filter funnel, measuring cylinder, large beaker, 1 m rule, pondweed.

      Content guidance

      • Risk assessment required - equipment

      Supervision

      Adult supervision required

      Licence

      This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

      Lesson video

      Skip lesson video

      Loading...

      Prior knowledge starter quiz

      Download quiz pdf

      6 Questions

      Q1.
      What are the products of photosyntheisis?

      Correct answer: glucose and oxygen
      carbon dioxide and water
      oxygen and carbon dioxide
      glucose and carbon dioxide

      Q2.
      As the pond plant shown below photosynthesises, bubbles form around its leaves. Which gas is in the bubbles?

      An image in a quiz
      Correct answer: oxygen
      carbon dioxide
      nitrogen
      hydrogen

      Q3.
      What is an independent variable?

      Correct answer: a factor that is changed during an experiment
      a factor that is kept the same during an experiment
      a factor that is measured during an experiment

      Q4.
      What is a control variable?

      a factor that is changed during an experiment
      Correct answer: a factor that is kept the same during an experiment
      a factor that is measured during an experiment

      Q5.
      When investigating the effects of light intensity on the rate of photosynthesis, which of the following are control variables?

      An image in a quiz
      Correct answer: temperature
      light intensity
      Correct answer: carbon dioxide concentration
      volume of gas collected

      Q6.
      Why is it important to control the temperature in this experiment?

      because temperature affects the amount of water
      because temperature affects the colour of the pondweed
      Correct answer: because temperature can affect the rate of photosynthesis
      because temperature can affect the ight intensity

      Assessment exit quiz

      Download quiz pdf

      6 Questions

      Q1.
      What is an accurate measurement?

      Correct answer: a measurement close to the true value
      a measurement taken quickly
      a measurement taken with a ruler
      a measurement using more equipment

      Q2.
      How can you use the equipment shown to measure the rate of photosynthesis?

      An image in a quiz
      Correct answer: Count the number of bubbles of oxygen produced in a specific period of time.
      Measure the volume of carbon dioxide produced in a specific period of time.
      Measure the volume of oxygen produced in a specific period of time.
      Count the number of bubbles of CO₂ produced in a specific period of time.

      Q3.
      How can you reduce the intensity of the light that the pondweed receives from the lamp?

      An image in a quiz
      Put a beaker of water between the pond weed and the lamp.
      Increase the brightness of the lamp
      Correct answer: Move the pondweed away from the lamp.

      Q4.
      What is the purpose of counting the bubbles produced by the pondweed?

      to measure the height of the pondweed
      to measure the amount of CO₂
      to measure the temperature of the water
      Correct answer: to measure the rate of photosynthesis

      Q5.
      What is the main limitation of counting bubbles to measure the rate of photosynthesis?

      it does not measure temperature
      it is too difficult
      Correct answer: it does not give an accurate volume of gas produced
      it is too quick

      Q6.
      What is a logical prediction for this investigation?

      An image in a quiz
      As distance increases, the rate of photosynthesis will increase.
      Correct answer: As distance increases, the rate of photosynthesis will decrease.
      As distance increases, the rate of photosynthesis will stay the same.

      Lesson appears in

      UnitBiology / Photosynthesis: factors affecting the rate

      AQABiology

      Show Foundation unit
      Show Higher unit

      OCRBiology

      Show Foundation unit
      Show Higher unit

      UnitCombined science / Photosynthesis: factors affecting the rate

      AQACombined science

      Show Foundation unit
      Show Higher unit

      OCRCombined science

      Show Foundation unit
      Show Higher unit