Michelle Flores, age 10, of Salt Lake City, Utah, for her question:

What gases are in the air?

Almost all of the air is a mixture of nitrogen gas and oxygen gas plus a little carbon dioxide and tiny traces of several other gases. Let's suppose we can separate the gases in ten quart bottles of ordinary air. There would be enough nitrogen gas to fill eight of the bottles and enough oxygen to fill almost two of them. This is almost ten full bottles. But there is just enough space left for some small helpings of about six other gases.

In this mixture of tiny traces, we would find a little carbon dioxide and some argon gas. We also would find traces of the gases neon and krypton, helium and hydrogen and maybe a little ozone. There also would be some gaseous water vapor. These are the gases in clean, pure air.