Eddie Ketarakis, age 12, of Casseyville, I11., for his question:

HOW DO YOU COMPRESS AIR?

You compress air by forcing it into a small space. A few small, strong cylinders can hold all of the air you find in a large room when proper pressure is applied.

The compressed air is made up of air molecules which increase in speed when placed under pressure. The air also becomes warmer.

You are actually compressing air yourself when you use your tire pump to fill your bike's tire. You'll notice that the pump becomes warmer as the air pressure increases.

Compressed air is used to inflate auto tires, to fill air mattresses and to operate pneumatic drills. In a submarine air is compressed to one two hundreths of its normal volume and is kept in cylinders. Air is then released into water filled ballast tanks and, as the water is forced out by the compressed air, the submarine becomes lighter and rises to the surface.