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

EVOLUTION OF OXYGEN


The best example is using pond weed (Elodea) which produces bubbles of O2 as it photosynthesises.
Method:
- Place 5 sections of Elodea under water in 5 different clear containers (a test tube works best)
- place each test tube at a certain distance from a lamp (for example, at 10cm increments where the first test tube is 10cm away from the lamp, then the 5th is 50cm away)
- Time 1 minute and count the number of bubbles that are produced from each test tube (the bubbles are oxygen, a byproduct of photosynthesis)

Should your experiment go to plan, you should conclude that the test tube closest to the lamp produced the most bubbles due to the fact that the rate of photosynthesis was highest because it was receiving light energy at the highest intensity (the more light energy received, the faster the rate of reaction, and therefore rate of photosynthesis, as the water and carbon dioxide molecules have more energy so they collide quicker/more)



PRODUCTION OF STARCH


A good example of an experiment that proves that light and CO2 are essential for the production of starch  is the Geranium plant. It’s leaves normally turn blue-black in the presence of iodine solution showing starch is present (you have to boil it in ethanol first to remove the chlorophyll to show the colour).
However, if one leaf is put in aluminum foil (removing light) and another is kept with lime water (removing CO2) both do not turn blue-black, implying both CO2 and light are essential for starch production and, therefore, essential for photosynthesis.