Exploring Perceptions of Temperature

Some materials feel cooler or warmer than others, even if they are the same temperature!

Materials:

• A variety of materials with a flat surface larger than your hand (metal(s), wood, plastic, Styrofoam, glass, and cardboard). Be sure one of the materials is a metal. Try a plastic cafeteria tray and a cookie sheet, for example.
  
  
• A thermometer. Liquid crystal thermometers work great for measuring the temperature of a surface. A cold bottle of soda pop with a pop-off cap or screw off lid.
  

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Procedure:

1. Leave the materials out in the room in the same location so that they will come to room temperature.
2. Place two of the materials side by side on a desk or table and place your palms down on each one and compare how hot or cold they feel.
3. Use a thermometer to check the temperature of each material.
4. Try two new materials and eventually order all of the materials you have gathered according to how warm or cool they feel.

Leading the Activity:
Explorations, Questions, and Sharing

• Which of the materials feels the coolest? warmest?
  
• After sitting in the same spot in your classroom, all of the materials should be the same temperature-even if one or more of them feel cooler than others. Do you believe that the materials are all the same temperature?

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Background:

Some materials conduct heat more efficiently than others. Metals are great conductors of heat and absorb heat from your hand easily while other materials conduct heat from your hand more slowly. The nerve endings in your palm sense the removal of heat from your hand as it cools and perceive that the material is cooler even though it is the same temperature. The materials appear to be different temperatures because they conduct heat away from your hand at different rates.

Credit where credit belongs...

This same activity, titled "Cold Metal" is one of the activities listed in the Exploratorium Science Snackbook Series -specifically in The Cool Hot Rod & other Electrifying Experiments on Energy & Matter by Paul Doherty, Don Rathjen and the Exploratorium Teacher Institute (Copyright by the Exploratorium, 1991, 1996 and published by John Wiley & Sons, Inc.). You can find all of these and more "Snackbook" activities at the Exploratorium's website: Don't miss 'em!

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