Required Practical 5 - investigate the effect of light on the rate of photosynthesis of an aquatic plant such as pondweed.

Question 1

Method Photosynthesis Practical

Answer 1

• Source of white light is placed 10cm away from pondweed
• Fill the boiling tube with sodium hydrogen carbonate solution which releases carbon dioxide
• Put a piece of pondweed into the boiling tube and with the cut end at the top
• Leave the tube for 5 minutes to acclimatise
• Start a stopwatch and count the number of oxygen bubbles per minute at each distance
• Change the distance and have it further each time

Question 2

If you use a light bulb for the experiment what do you need to do

Answer 2

Place the test tube in a beaker so the beaker absorbs the heat produced by the bulb or use an LED light because they don’t produce heat

Question 3

How can you make more reliable results

Answer 3

Repeat the experiment and calculate a mean amount of bubbles from each distance

Question 4

Problems of this experiment

Answer 4

Number of bubbles can be too fast to count , bubbles are different sizes so you would be counting a big and small bubble as equal

Question 5

How to solve the problems

Answer 5

By measuring volume of oxygen produced by placing the weed under a funnel and catch the bubbles in a measuring cylinder