Hank Ratliff, age 15, of  Patterson, N.J., for his question:

WHAT IS LIQUID AIR?

Liquid air is air so cold that it has changed from a gas to a liquid.

Air becomes a liquid at about minus 312 degrees Fahrenheit. This temperature is so low that liquid air actually boils when it comes into contact with warmer substances, such as ice. The liquid air boils because the ice is much hotter than it is.

Liquid air can freeze substances that do not freeze in even the coldest weather.

You'll find that liquid air looks much like water. It is clear and slightly blue. It is made of the same chemical elements as ordinary air, but its elements are liquids instead of gases.

Nitrogen makes up about four fifths of the volume of liquid air. Oxygen makes up about one fifth. Small amounts of other elements such as argon, neon and helium are also present.