New
New
Year 11
AQA
Higher

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.

New
New
Year 11
AQA
Higher

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.

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

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.

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

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 (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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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

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.

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