required practical: rate of photosynthesis

measuring the oxygen production of a plant

what is the method for finding the effect of light intensity on the rate of photosynthesis?

1. set up a boiling tube containing sodium hydrogencarbonate

2. cut a piece of pondweed and use forceps to place it in the boiling tube

3. position the boiling tube 10cm from the light source and wait for 5 minutes

4. start a stopwatch

5. count the number of bubbles from the cut end of the stem in one minute

6. repeat the experiment at different distances from the light source and calculate the average number of bubbles produced per minute

independent variable

distance from the light source/light intensity

dependent variable

the number of bubbles produced per minute

control variables

• temperature

• using the same piece of pondweed

what is light intensity measured in?

lux

how can the experiment be changed?

• different concentrations of sodium hydrogencarbonate

• different temperatures of water