Gaining and Losing Heat Energy: Can You Feel It?
 

	Fun Experiment to Try at Home!
		Purpose To determine how conduction makes one object feel cool and another warm even if they are at the same temperature.   Materials - empty metal can (a soda can will work) - Styrofoam cup   Procedure 1.  Allow the can and the cup to sit on a table for five minutes or more so that each comes to room temperature. 2. Hold the can in one hand and the Styrofoam cup in the other. 3. Compare how cool or warm the can and the Styrofoam cup feel.   Sum It Up! The metal can and the Styrofoam cup are both at room temperature, which is less than the temperature of your body. Thus, when you touch the can and the cup, the heat from your skin is transferred to them. But because the metal can is a better conductor, the heat from your skin flows into the metal can and is carried to other parts of the can at a faster rate than in the Styrofoam cup. Since the metal surface being touched does not warm quickly, heat continues to be lost from your skin and the metal can feels cooler to the touch than the Styrofoam. In time the can would be heated and would no longer feel cold.

You have tiny thermometers in your skin.
 
In your skin are temperature-sensitive nerve endings that act like tiny thermometers: they can detect differences between the temperature inside and outside of your body. Heat is a form of energy that always flows from a hotter surface to a colder surface. If you touch an object that is warmer than your skin, heat is transferred from the object to your skin. Your skin sensors send a message to your brain that your skin is receiving heat. Depending on the amount of heat you receive, your brain can determine whether an object is hot or cold. If an object is colder than your skin, heat is transferred from your skin to the object. Your skin loses heat, and your brain determines that the object is cold. In other words, whether something feels cold or hot depends on whether your skin loses or gains heat.

All materials conduct heat, which means that molecules bump into each other and transfer heat. But not all materials conduct heat at the same speed. Conductors are materials that conduct heat quickly, and insulators are materials that conduct heat more slowly.

For more information about touch and other senses, see "Janice VanCleave's Human Body for Every Kid." (New York: Wiley, 1995)