This week's experiment is a continuation of experiment #488, Cooling Fans. While the fan just moves air around, you can actually use it to help cool the room.

For this investigation, you will need:

- two washcloths
- water

Wet one of the washcloths, and squeeze out the excess water. Place the wet washcloth and the dry washcloth where you can easily reach them. Place one hand on the table. Pick up the dry cloth in your other hand. Gently fan the cloth over your hand, and notice how cool your hand feels. Then do exactly the same thing with the wet cloth. You should notice that the air moved by the wet cloth makes your hand noticeably cooler. Why?

Think back to the reasons why a fan makes you feel cool. Evaporation! As moisture from your skin evaporates, it absorbs heat from your skin, making you cooler. As you fan your hand with the wet towel, water from the towel is evaporating. As it evaporates, it absorbs heat from the air around it, making the air cooler. This cooler air blows across your skin, making you feel cooler.

If you are ever stuck without air conditioning, open two windows so you will get a breeze through the room. In front of the window where the air is entering the room, hang one or more wet towels. As the breeze evaporates the water from the towels, the air in the room will be cooler.

Of course, you could also cool yourself by holding a bowl of ice cream against your skin, but that works better if the ice cream is cooling you from the inside.