Thermal Energy and Conduction - "Strong Coin"

Standard

NSES Content Standard B - Physical Science: Properties of matter, motion and forces, and transfer of energy - Grades 5-8

The understanding of energy in grades 5-8 will build on the K-4 experiences with light, heat, sound, electricity, magnetism, and the motion of objects. In 5-8, students begin to see the connections among those phenomena and to become familiar with the idea that energy is an important property of substances and that most change involves energy transfer. Students might have some of the same views of energy as they do of force--that it is associated with animate objects and is linked to motion. In addition, students view energy as a fuel or something that is stored, ready to use, and gets used up. The intent at this level is for students to improve their understanding of energy by experiencing many kinds of energy transfer.

Misconceptions

• Ice cannot change temperature

• When the temperature of a boiling substance remains constant, something is “wrong.”

• The bubbles in boiling water contain “air,” Oxygen,” or “nothing,” rather than water vapor.

• All liquids boil at 100°C (212°F) and freeze at 0° C (32°F).

• Heat is a substance.

• Heat is not energy.

• Temperature is a property of a particular material or object (metal is naturally colder than plastic).

• The temperature of an object depends on its size.

• Heat and cold are different, rather than being opposite ends of continuum.

• Boiling is the maximum temperature a substance can reach.

• Objects of different temperatures that are in constant contact with each other, or in contact with air at a different temperature, do not necessarily move toward the same temperature.

• Heat only travels upward.

• Heat rises.

• The kinetic theory does really explain heat transfer. (It is recited, but not believed.)

• Objects that readily become warm (conductors of heat) do not readily become cold.

• All solids expand at the same rate.

Activity

“Strong Coin” is a routine I developed for birthday parties and public events shows. A “strong” member of the audience is asked to come up to the front. On a table is a plastic plate with 5 US quarters equally spaced on it. With the magicians back turned to the audience and the plate, the volunteer is asked to choose a coin and show it to nearby members of the audience. Then, they are asked to tightly hold the coin in their hand as they shake it and do a variety of silly dance moves and wiggles. They are then asked to return the coin to the plate just as they found it. The magician walks over to the volunteer, gives them a loud sniff, and they proceeds to “smell” each coin one at a time until they “smell” the one the “strong” volunteer was holding.

The illusion comes from the selling of this as a “smelling” activity. When the coin is “smelled” it is held under the nose and in contact with the upper lip. The upper lip on of the most temperature sensitive places on the human body and the coin that was help by the volunteer will have heated up considerably by the time they return it to the plate.

It’s not magic, it’s science!

This activity focuses students’ attention on the ideas that temperature is not a property of a particular material, temperature is not size dependent, heat travels from one object to another by multiple means, the transfer of energy does not always occur at the same rate, objects that are in contact move towards the same temperature, and objects that warm-up easily, cool down easily.