How to prove that Photosynthesis needs Carbon dioxide

Most of us learn in school at a very young age that plants produce food using the process of photosynthesis. We know that the process involved the interaction of the green pigment known as chlorophyll and the presence of the gas carbon dioxide. Now in this science project we are going to attempt to prove these facts.

We will use two as close to identical plants to begin the experiment. Have them potted in identical pots as well which can be covered with a bell jar. It is transparent but does not allow outside air in. Now here is how we will proceed. One plant will be given plenty of carbon dioxide while the other one will be starved of the essential gas.

In the first bell jar with the plant under it light a candle and leave it to burn off all the oxygen. This plant under the bell jar will have a large supply of carbon dioxide. The other bell jar with the plant under it will have a dish with caustic soda. The caustic soda will absorb all the carbon dioxide in the air and the plant will have access to none. Seal the bell jars with petroleum jelly.

Now leave the plants undisturbed for a day. After that you will notice that the plant which had access to carbon dioxide has more starch in its leaves than the one that did not have any carbon dioxide with it under the bell jar. Quite an interesting science project.