We'll do some testing with balloons, to see some of the differences among air, carbon dioxide, and helium.

This project is best done inside the classroom. If we do it outside, our project materials will be swept away into the heavens!

We need a helium-filled balloon. We can purchase a small tank of helium from a chemical supply house, just for this purpose. Then, we need to buy some balloons, all of the same size. We will use three balloons each time we do this project.

Collect carbon dioxide in a balloon, inflate the second balloon with helium, then fill up the third balloon with air so they all are inflated to the same circumference.

Toss the balloons in the air, and observe what happens.

Release all three balloons at the same time.

You will be able to judge that different gases have different weights.