You can experiment with balloons to determine if air has weight.

In this investigation you'll conduct an experiment using a balance scale to determine if air has weight. First you'll build your balance scale. Then you'll weigh two balloons without any air in them. Next you'll inflate one balloon and place it on the balance scale to see what happens.

What you'll need:

Thread or string
A bamboo skewer or a straw
Two paper clips
Two balloons of the same size and shape (they can be different colors)

Assembly:

1. Start by tying approximately twelve inches of thread to the center of the skewer. Adjust the thread on the skewer until it is balanced.
   
2. Bend your paper clips so they look like a hook.
   
3. Tie a paper clip to each end of the skewer with about three inches of thread. Make sure it is still balanced.
   
4. Attach a balloon to each paper clip on each end of your balance scale.
   

Investigate:

If the balloons are the same size the balance scale should be balanced.

Now inflate one of the balloons and tie it. Then attach it to the paper clip on one end of the balance scale. The other end should still have your other deflated balloon on it.

What happens?