If you didn't know how to test for the presence of sugar and starch, what chemical gas could you try to research a test for in order to determine if a plat is photosynthesizing? why?

Plants use green pigments called chlorophylls to trap light energy. The
chlorophylls give a plant its green color. Inside the cells that have
chloroplasts, the light energy is used to make a simple sugar called glucose.
The process by which plants use light energy to make glucose is called
photosynthesis.

During this process of sugar production, carbon dioxide combines with water to
form glucose and oxygen is released. Oxygen that is produced in photosynthesis
is given off as a gas. If a lot of oxygen is being given off, photosynthesis is
occurring rapidly. If little oxygen is being given off, photosynthesis is
occurring slowly. The amount of trapped light energy and the amount of carbon
dioxide available affects the rate of photosynthesis.

The purpose of adding sodium bicarbonate powder to the water increases the
amount of carbon dioxide in the water.                 hope this helped

This investigation can be performed with water plants grown in many parts of
the world, except regions that have permanent ice.

They are all full and don't need any more electrons in there outer shell.