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You’ve probably noticed that we humans get sweaty when it’s hot out, or after we’ve had a hard workout, or just worked hard. Sweat cools us off when our body temperature rises. How does warm water (sweat) make us feel cooler? Get your feet wet with this experiment and find out!

What You Need

  1. one pair of athletic socks
  2. a fan

What You Do

  1. Wet the foot of one sock with warm water, wringing it out so it’s damp, not drippy.
  2. Put on the socks, with one foot in a wet sock, and one foot in a dry sock.
  3. Set up a place to sit for a while with the bottoms of your feet facing the blowing fan, and settle down for about 5 minutes.
  4. Does the foot with the wet sock feel different from the foot with the dry sock?

Muy Importante!

Keep your feet away from the fan blades!

What's Happening?

As the fan blows, the water in the damp sock evaporated. The heat of your foot gave the liquid molecules a little energy and they changed from slow moving liquid to fast moving gas molecules. As the water in the sock evaporated into the air, it carries heat energy with it. The heat comes from your foot, so your foot cools down! Sweat works the same way – the heat energy from your body gets transferred to your sweat and then into the air as the water in your sweat evaporates. Sweat is cool!

Bill Nye