Starter quiz
- Wat are the reactants in photosynthesis?
- carbon dioxide and water ✓
- glucose and oxygen
- water and oxygen
- carbon dioxide and glucose
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- As algae photosynthesise, what will happen to the concentration of carbon dioxide in the water?
- it decreases ✓
- it increases
- it remains constant
- it fluctuates randomly
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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 ✓
- number of algal beads ✓
- light intensity
- change in pH
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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 change in the pH, shown by the indicator of the indicator.
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- Why does photosynthesis lead to a colour change in the indicator solution?
- Photosynthesis gives out carbon dioxide which makes solutions more acidic.
- Photosynthesis uses carbon dioxide which increases the pH of the solution. ✓
- Photosynthesis releases glucose, altering the solution's colour.
- Light absorbed by the algal beads reacts with the indicator solution.
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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 pondweed and the lamp.
- Increase the brightness of the lamp.
- Move the pondweed away from the lamp. ✓
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- If the indicator changes from cherry red to purple, what does this tell you about the rate of photosynthesis?
- there is no photosynthesis occurring
- photosynthesis is happening at a low rate
- photosynthesis is happening at a high rate ✓
- photosynthesis has stopped completely
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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 colour change of indicator.
- Accurate measurement of variables (distance, time, colour change); control of variables that might affect the results.
- Comparison of indicator colour to a chart to determine pH.
- 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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