Richard Stuber, age 9, of Louisville, Kentucky, for his question:

What is Freon?

This is the working chemical they use inside an electric refrigerator. There it works to change trays of water into solid cubes of frozen ice and to chill the food items sealed in the box. This busy chemical also is the filmy squirt that comes out of a bug killing aerosol can.

Every up to date nine year old knows that our world is made of tiny atoms and molecules, much too small for human eyes to see. There are only about 100 different atoms, but assorted atoms package themselves together in thousands of different mole¬cules. Each type of atom and each type of molecule has its rules for behaving, but smart human minds have figured out how and why these midgets behave as they do. We have used the rules to perform a few tricks of our own and even packaged assorted atoms to create man made molecules. One of these very useful man made chemicals is Freon.

We give Freon a capital letter because it is a trade name that belongs to the Dupont Chemical people who created it. Their lab men improved it, and itow Freon is the name of a whole family of gassy chemicals. Each molecule in the family is an assort¬ment of atoms of fluorine, chlorine and carbon    tied up in a very special package arrangement. Like all chemicals, man made Freon has rules of its own    in fact, a whole bag of tricks that makes it very useful to us.

For one thing, it keeps miniature specks of other chemicals separate from each other. We can add tiny droplets of bug killer to Freon and cram the mixture into an aerosol can. Press the button and out it squirts with a fine spray of deadly chemicals aimed at the pesky insect world. Freon is even more useful when put to work in an electrical refrigerator. A compressor gadget can squeeze and condense its separate gas molecules into liquid Freon. When the gadget frees the liquid, the pressure is off    and the eager molecules are free to separate and zoom apart again into spreading Freon gas. In an electric refrigerator, the working gadgets change the Freon back and forth from liquid to gas and keep it cycling around and around through the pipes. The switch from liquid to gas chills the food inside because molecules use heat to move around. Gas molecules need more heat because they move faster than liquids. When a liquid becomes gas, it grabs extra heat from things around it    and they grow cooler. When liquid Freon leaves the pressure chambers, its molecules are freed to spread out through the pipes in the walls. They grab heat from inside the box and separate themselves into Freon gas. The food items are chilled and the Freon gas cycles back for another squeezing. As it: condenses back to a liquid, it gives up the heat it stole from inside and prepares for another useful trip through the pipes.

The up to date Freons are safe gases. They do not rust metals or burn. You cannot see or sniff them. The whiff from an aerosol can comes from the chemical droplets that the Freon sprays around. A gas used to chill things is called a refrigerant. Lab men can squeeze many gases to release them back to heat stealing gases. But in most cases this takes too much pressure to make the job worth while. Only a small compressor run by a little electric power is needed to condense Freon gas. This is the main reason why this man made chemical is rated as a tip top refrigerant for everyday work.