the amount of light reaching a given surface area in a period of time

a measure of how much change occurs per unit of time

a factor that can be changed during an experiment

a factor that is kept the same during an experiment

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

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

Combined science

Pupils learned about ways in which the human body maintains a constant internal environment in response to internal and external change, including changes in temperature and water balance.

This unit explores factors affecting photosynthesis rates and focuses on planning and conducting experiments. It includes selecting techniques, accurate measurements, data analysis, and evaluating methods to improve reliability and suggest further investigations.

Photosynthesis: factors affecting the rate

Physical activity and equipment requiring safe use

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.

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

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.

Why does photosynthesis lead to a  colour change in the indicator solution?

Put a beaker of water between the pondweed and the lamp.

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

photosynthesis is happening at a low rate

photosynthesis is happening at a high rate

If the indicator changes from cherry red to purple, what does this tell you about the rate of photosynthesis?

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.

What is a logical prediction for this investigation?

As algae photosynthesise, what will happen to the concentration of carbon dioxide in the water?

a factor that is changed during an experiment

a factor that is measured during an experiment

 a factor that is changed during an experiment

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

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

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

Content guidance

Risk assessment required - equipment

Adult supervision required

This lesson will be removed by end of Summer Term 2025.

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

Lesson outcome

Content guidance

This lesson will be removed by end of Summer Term 2025.