| In the summertime, have you ever gotten out of a | | | | 1. A gas cools on expansion. |
| swimming pool and then felt very cold standing in the | | | | 2. When you have two things that are different |
| sun? That's because the water on your skin is | | | | temperatures that touch or are near each other, the |
| evaporating. The air carries off the water vapor, and | | | | hotter surface cools and the colder surface warms up. |
| with it some of the heat is being taken away from | | | | This is a law of physics called the Second Law of |
| your skin. | | | | Thermodynamics. |
| This is similar to what happens inside older | | | | Old Refrigerators |
| refrigerators. Instead of water, though, the refrigerator | | | | If you look at the back or bottom of an older |
| uses chemicals to do the cooling. | | | | refrigerator, you'll see a long thin tube that loops back |
| There are two things that need to be known for | | | | and forth. This tube is connected to a pump, which is |
| refrigeration. | | | | powered by an electric motor. |