Gay Simmons, age 12, of Albany, N. Y, for her question:
How does a refrigerator work?
Cold is merely an absence of heat. The food in the refrigerator will become cool because its boat is stolen. This heat thief is a man‑made chemical called a refrigerant. Ice is a simple refrigerant and, not so long ago, an icebox was really an icebox. The ice man came along every few days and placed a chunk of ice in it. The ice stole heat from the food and used this heat energy to melt itself into water.
Sweat is one of Mother Nature’s oldest refrigerants. When your body becomes too warm the sweat glands pour out moisture onto the skin. This moisture evaporates. The liquid becomes gas. In order to do so it needs heat energy, dust as solid ice needs heat energy to change into water. The sweaty moisture on the body uses heat from the skin and surrounding air. As it evaporates, the skin and blood vessels near the surface become a little cooler.
The old style ice box was a sloppy sort of contraption, drip‑dripping water into a pan. When all the ice melted new ice was needed. There was no way of using it aver again. In a modern refrigerator the refrigerant is used over and over again. This refrigerant is not a solid block of ice which changes into liquid water. It is a liquid chemical which changes into gassy vapor. A machine in the refrigerator changes the gas back again into a liquid.
In most refrigerators the gas is a powerful, man‑made chemical called Fre on. Nature did not create a perfect refrigerant, one that was safe, powerful and fast‑acting. The chemists had to invent one by rearranging the atoms in molecules. The result, known as Freon 12, is fast‑acting, powerful enough to freeze water and it will not burn, explode or eat away the metal pipes.
This is the man‑made chemical that evaporates from liquid to gas and back again in the modern refrigerator. It runs through the coiled tubes around the ice trays, stealing heat from everything inside the white box. The liquid Freon uses up this heat to turn itself into gas.
The refrigerator then has the job of turning the gaseous Freon back into its liquid form. The first step is pressure. The gas is squeezed closer together. Step two cools this compressed gas. This job is done by a powerful fan in the refrigerator. The compressed gas then gels into droplets of liquid.
The liquid refrigerant collects in coiled tubes below the food box. It runs up other tubes to the coils around the ice trays. It expands as it goes and becomes a gas. This process uses up heat. The gaseous refrigerant now runs down to the machinery below the food box. There it is compressed and cooled again to liquid form. It is now ready to make another trip around the food box, turning to gas and stealing heat as it goes.