Sonoran Desert

Try This

Sweat Effect

What it does

This experiment shows how sweating helps keep your body cool.

What you need

• an outdoor thermometer
• cotton ball
• rubbing alcohol
• watch

What to do

1. Put the thermometer on your table or work surface for about five minutes so that it will register at room temperature. Observe this temperature.
2. Wet the cotton ball with alcohol.
3. Spread a thin layer of the wet cotton across the bottom bulb of the thermometer
4. Blow lightly on the wet cotton for about 30 seconds. Watch what happens to the temperature reading.

What it's all about

The temperature goes down as you blow on the wet cotton, because the alcohol on the cotton is evaporating. Evaporation occurs when a liquid absorbs enough heat energy to change into a gas. In this experiment, the alcohol takes heat energy from the mercury in the thermometer. This causes the mercury to contract and move down the thermometer, giving a lower temperature reading.

When it's hot outside, your body releases liquid from the sweat glands on your skin. As the liquid—sweat—evaporates, it removes heat from your skin and makes you feel cooler.

Remember, be sure you have a parent, teacher, or other adult help you!

Sweating is just one of the ways that people and animals keep cool in the desert.
Read about it.