Light intensity Practical

Question 1

How can you measure the effect of light intensity on the rate of photosynthesis?

Answer 1

measuring the change of pH in solution around algal balls

Question 2

Why does the pH change?

Answer 2

CO2 forms an acidic solution, and photosynthesis changes the CO2 concentration in the solution

Question 3

Explain why rate of change in pH is a measure of the rate of photosynthesis in this experiment.

Answer 3

CO2 is taken in by plants when they photosynthesise. Removing CO2 from the solution will increase its pH.
The rate of change in pH will indicate the rate at which CO2 is removed from the solution.

Question 4

Explain why using a water tank is important if the lamp has a hot bulb.

Answer 4

Temperature also affects the rate of photosynthesis. If temperature is not controlled, then it will change with distance and so confuse the results.

Question 5

A student covered one tube of algal balls in kitchen foil and placed it close to the tank as an addition to the practical.
Explain the purpose of the tube.

Answer 5

The tube will act as a control as it should show no change in pH as there will be no photosynthesis in the tube.