Introduction:
Photosynthesis is a vital process for plants as it allows them to convert light energy into chemical energy. Carbon dioxide is essential for photosynthesis as it is one of the key reactants required for this process to occur.

Activity:
To demonstrate the importance of carbon dioxide in photosynthesis, you can set up a simple experiment using a plant, water, and a source of light. Here's how you can do it:
1. Setup: Place a healthy plant in a transparent container filled with water. Ensure that the plant has access to sunlight or a source of light.
2. Control Group: Keep one container with the plant and water only (without any added carbon dioxide).
3. Experimental Group: In another container with a similar setup, introduce carbon dioxide by either blowing air into the water or adding a small amount of baking soda.
4. Observation: Over the next few days, observe the plants in both containers. You will notice that the plant in the experimental group (with added carbon dioxide) will show signs of healthy growth, such as greener leaves and increased size, compared to the plant in the control group.
5. Explanation: The plant in the experimental group thrives because carbon dioxide is a crucial reactant for photosynthesis. During photosynthesis, plants use carbon dioxide, water, and light energy to produce glucose and oxygen. Without an adequate supply of carbon dioxide, the plant's ability to carry out photosynthesis and produce food is limited, resulting in stunted growth.
By conducting this experiment, you can visually demonstrate the importance of carbon dioxide in the photosynthesis process and its impact on plant growth.