Bioenergetics RQP- effect of light intensity on the rate of photosynthesis

Question 1

apparatus diagram

Answer 1

• lamp facing test tube with pondweed and water in, ruler underneath from lamp to test tube
• tubing coming out of test tube connected to a syringe
• ruler near tubing (for measuring O2 bubbles)

Question 2

step 1

Answer 2

Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.

Question 3

step 2

Answer 3

Cut a piece of the pondweed 8 cm long.

Question 4

step 3

Answer 4

Use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don’t damage the pondweed, or cause the liquid to overflow.

Question 5

step 4

Answer 5

Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.

Question 6

step 5

Answer 6

Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.