By: Tom Wickersham

THE SCIENCE OF COOLING OFF

With temperatures soaring into the triple digits this past week, we often turn to the comfort of our air-conditioned homes, movie theaters or shopping malls to beat the heat.

Some prefer the cooling sensation of diving into swimming pools, jumping through sprinklers or swimming in rivers.

Have you considered why water helps us cool off? Even just a spray from a squirt bottle helps to cool down. In order to help understand why water (and other liquids) offer this cooling capability, try the following experiment:

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For this experiment you will need water, rubbing alcohol, cooking oil and paper towels. First, blow on the back of your hand. Notice how it feels.

Next, using the water, lightly wet the back of your hand. Again, blow on your hand. Do you notice a difference?

Using a paper towel, dry the back of your hand and try the experiment again, this time with rubbing alcohol instead of water. Notice the temperature change when you blow on your hand.

Dry your hand again and try it once more, this time with cooking oil. Again, blow and notice the temperature sensation.

What did you discover? When you blew on the wet skin, it felt cooler than the dry skin. When you blew on the skin with alcohol, it was much cooler. When you blew on the skin with oil, did you notice any difference than with dry skin?

The cooling sensation you feel, when you stand in front of a fan or just blow on the back of your hand, is due to evaporation. As a liquid evaporates, it absorbs heat from its surroundings. This produces a cooling sensation on your skin. The faster the liquid evaporates, the cooler it feels. Since the oil does not evaporate, it does not produce a cooling sensation. (Wouldn't it be nice to run through a sprinkler of rubbing alcohol? It sure would be cool, but otherwise, probably not too safe).

Of course the human body naturally produces its own moisture to help us cool down. It's called persperation. When you get hot, you sweat. Unlike a dog that needs to pant to cool down, humans produce large amounts of sweat to help their bodies keep cool.

This experiment comes from Robert Krampf's experiments of the week. For more information, contact him at krampf@aol.com.

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Plan a cool venue for your Independence Day festivities. Visit Explorit Science Center tomorrow to learn more about gardens and plants when you visit "How Does My Garden Grow?" Keep in mind that in honor of our nation's holiday, Explorit will be closed on Sunday, the fourth of July. Explorit will be open for business as usual on Monday, July 5.

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Explorit Science Center is located at 3141 5th Street in East Davis. The current exhibition is How Does My Garden Grow? Public hours are Saturday from 11:00 a.m. to 4:30 p.m., Sunday from 1:00 to 4:30 p.m., and Tuesday through Friday from 2:00 to 4:30 p.m. Regular admission is $3; members, teachers (with school ID) and children under 4 are free.