PAGS

Question 1

Write a method for measuring how light intensity affects photosynthesis and state any control variables. (6)

Answer 1

1) Place the plant in the conical flask of water with the sodium hydrogen carbonate solution. Cut plant at an angle to prevent air being trapped.
2) Place the flask in front of the light source at a set distance using a meter ruler eg 100cm.
3) Attach the gas syringe to conical flask
4) Leave for a certain period of time.
5) Record the amount of gas produced.
6) Move the lamp source or the light source 10cm closer and measure volume of gas produced over a fixed period of time eg 90cm, 80cm, 70cm.

Control variable:

• same period of time for gas to be produced.
• use the same gas syringe.
• use same light bulb.
• flask has the same sized piece of pondweed.