Starter quiz
- What are the products of photosyntheisis?
- glucose and oxygen ✓
- carbon dioxide and water
- oxygen and carbon dioxide
- glucose and carbon dioxide
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As the pond plant shown below photosynthesises, bubbles form around its leaves. Which gas is in the bubbles?- oxygen ✓
- carbon dioxide
- nitrogen
- hydrogen
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- What is an independent variable?
- 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
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- What is a control variable?
- 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
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When investigating the effects of light intensity on the rate of photosynthesis, which of the following are control variables?- temperature ✓
- light intensity
- carbon dioxide concentration ✓
- volume of gas collected
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- 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
- because temperature can affect the rate of photosynthesis ✓
- because temperature can affect the ight intensity
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Exit quiz
- What is an accurate measurement?
- a measurement close to the true value ✓
- a measurement taken quickly
- a measurement taken with a ruler
- a measurement using more equipment
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- How can you use the equipment shown to measure the rate of photosynthesis?
- 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.
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- How can you reduce the intensity of the light that the pondweed receives from the lamp?
- Put a beaker of water between the pond weed and the lamp.
- Increase the brightness of the lamp
- Move the pondweed away from the lamp. ✓
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- 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
- to measure the rate of photosynthesis ✓
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- What is the main limitation of counting bubbles to measure the rate of photosynthesis?
- it does not measure temperature
- it is too difficult
- it does not give an accurate volume of gas produced ✓
- it is too quick
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What is a logical prediction for this investigation?- As distance increases, the rate of photosynthesis will increase.
- As distance increases, the rate of photosynthesis will decrease. ✓
- As distance increases, the rate of photosynthesis will stay the same.
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Worksheet
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Presentation
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Video
Lesson Details
Key learning points
- Following an appropriate method to vary light intensity and measure the gas given off
- Accurate measurement of variables (distance, time, amount of gas) and control of variables that might affect the results
- Counting bubbles and measuring volume of gas given off
- 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
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