Just like we have to drink water, we have to breathe air in to get the oxygen we need out of it. When we breathe out, we exhale carbon dioxide. Carbon dioxide is what is left after our bodies use the oxygen. But the air we breathe in and breathe out has other things in it, too. Some are good; some are not. Do you know what is in the air you breathe besides oxygen and carbon dioxide? This experiment will tell you if the air in your community clean.

You will need

• Eight natural rubber bands (Some rubber bands are not made of real rubber; make sure your rubber bands are real rubber. Your parents or teacher can help you find the right kind of rubber band.)
• Two wire coat hangers or two long pieces of wire that you can bend
• A large plastic bag
• Tape
• A magnifying glass
• A place outside to hang something up that is shady all the time

Here's what you do.

1. Bend each coat hanger into a rectangle (or make two rectangles using the wire). If you make rectangles out of wire, you need to make a hook (like a coat hanger hook) at one end of the wire.
2. Slide four rubber bands onto each rectangle. Be sure they are stretched tight. You can bend the rectangles out to tighten the bands if you need to.
3. Hang one rectangle up outside in the shady place. Be sure it is shady all the time; that is very important.
4. Put the other rectangle in the plastic bag. Seal the bag tightly with tape. Keep the sealed bag indoors in a drawer.
5. Wait a week.
6. When a week is up, check out the rubber bands you hung outside. Look at them carefully with the magnifying glass. Pull on one of them to stretch it. Write down what you see and what happens when you stretch the rubber band.
7. Look at the rubber bands you kept in the bag inside. Stretch one of them. Write down what you see and what happens.
8. If the rubber bands from outdoors are still in good shape, hang them outside for a few more weeks. Watch what happens to them.

Questions to Answer

If the air in your community is dirty, the rubber bands will break down and come apart very quickly, in just a few weeks. If the air is clean, the rubber bands will eventually come apart but it will take a very long time.

• What did the rubber bands look like in one week?
• What happened when you stretched the two rubber bands?
• How were the bands kept outside different from the ones kept inside?
• What did they rubber bands from outside look like in two weeks?
• What does this tell you about the air in your community?
• If your air is polluted, what makes it polluted?
• If you don't know what makes it polluted, how can you find out?
• What can you do to clean up your community's air?
• What can you do to keep it clean?