2.22 Describe experiments to investigate photosynthesis, showing the evolution of oxygen from a water plant, the production of starch and the requirements of light, carbon dioxide and chlorophyll

The most common one to use involves pond weed. Basically, it's placed under water and various different factors are varied (NOT at the same time)
Different variables you could change:

• The distance between the pond weed and a lamp (which would be it's source of light), is varied
• Baking powder is added to the water (increasing the amount of CO2)
• The amount of chlorophyll in a plant (a plant with white leaves could be compared to one with green leaves, as the green one will contain more chlorophyll)

Then you would measure the amount of gas given off (by counting bubbles or by downwards displacement). If there is more gas produced the rate of photosynthesis will be quicker. The production of starch can also be tested by adding iodine.