The effect of light intensity on rate of photosynthesis in algae: practical
I can carry out an investigation into the effect of light intensity on the rate of photosynthesis in algae.
The effect of light intensity on rate of photosynthesis in algae: practical
I can carry out an investigation into the effect of light intensity on the rate of photosynthesis in algae.
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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.
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.
Equipment
Light source, beaker, bijou bottles, hydrogencarbonate indicator, measuring cylinder, algae immobilised in alginate beads, graduated pipette, spatula, pH indicator chart, foil, meter rule, stopclock.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Wat are the reactants in photosynthesis?
Q2.As algae photosynthesise, what will happen to the concentration of carbon dioxide in the water?
Q3.What is an independent variable?
Q4.What is a control variable?
Q5.When investigating the effects of light intensity on the rate of photosynthesis, which of the following are control variables?
Q6.Why is it important to control the temperature in this experiment?
Assessment exit quiz
6 Questions
Q1.What is an accurate measurement?
Q2.How can you use the equipment shown to measure the rate of photosynthesis?
Q3.Why does photosynthesis lead to a colour change in the indicator solution?
Q4.How can you reduce the intensity of the light that the pondweed receives from the lamp?
Q5.If the indicator changes from cherry red to purple, what does this tell you about the rate of photosynthesis?
Q6.What is a logical prediction for this investigation?