Physicist: “Making cold” is impossible, so a “refrigerator” is really just a heat pump. Essentially, the gas gains energy from the moving piston the same way that a tennis ball gains energy from a moving racket or a baseball gains energy from a moving bat. 1) A (very) cold gas moves through the tubes in the back of the freezer, absorbing heat. The tubes absorb heat because, as cold as the freezer is, the the tubes are colder. 4) The compressed, room-temperature gas now passes through an expansion valve (which is a fancy word for “spray nozzle”).