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# Insulators

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Source:
Author: Janice VanCleave

### Purpose

To test the thermal conductivity of paper cups.

### Materials

• marker
• four 10-ounce (300-mL) paper cups-two made for cold drinks, two made for hot drinks
• 3 ice cubes of equal size
• saucer
• timer

### Procedure

1. Use the marker to label the cold-drink cups "A" and the hot-drink cups "B."
2. Put an ice cube inside an A cup and another ice cube inside a B cup. Put the remaining ice cube in the saucer.
3. Slip the second A cup inside the A cup with the ice cube so that the second cup rests on top of the ice cube. Repeat this step with the B cups.
4. After 5 minutes, look at the ice in the saucer. Then lift the top cup of each set to observe the ice cubes inside the closed cups. Continue making observations every 5 minutes until all the ice cubes completely melt. Record your observations in a Melting Time Data table like the one shown. Use a check mark to indicate the presence of ice and an X to indicate the absence of ice. Determine the number of minutes it took for the ice in the saucer and the closed cups to melt.

### Results

The ice cube in the saucer melts first, in the cold-drink cup second, and in the hot-drink cup last.

### Why?

Ice has a low internal energy (energy that indicates how hot or cold an object is). Heat is energy that flows from a material of high internal energy to a material of lower internal energy. The temperature of an object increases when heat flows into it and decreases when heat flows out of it. One type of heat transfer is called conduction, which occurs when molecules bump into each other, transferring heat from one molecule to the next. Heat is transferred faster through some materials and slower through others. Thermal conductivity is the measure of how fast heat flows through a material. The greater the thermal conductivity of a material, the faster heat flows through it.

Insulators like the hot-drink cups are materials that have low thermal conductivity, and conductors like the cold-drink cups are materials that have high thermal conductivity. In this investigation, you compared the thermal conductivity of two types of paper. The ice cube in the saucer was used as a control to determine if the cup materials affected the melting of the ice. Since the ice in the insulated paper cup took longer to melt, you can conclude that the insulated paper cup had lower thermal conductivity than the uninsulated paper cup. The paper in the hot-drink cup is a better insulator than is the paper in the cold-drink cup.

### For Further Investigation

The air in the closed cups was not able to move as freely as the air above the saucer. Is trapped air a good insulator? A project question might be, How does the motion of air affect its thermal conductivity?

Repeat the investigation, adding a third set of cups made of Styrofoam. While paper may have some trapped air between the fibers, Styrofoam has a great deal of trapped air in it. Be sure the Styrofoam cups are the same size as the paper cups.

### References and Project Books

Doherty, Paul, and Don Rathjen. The Cool Hot Rod and Other Electrifying Experiments on Energy and Matter. New York: Wiley, 1991.

Franklin, Sharon. Power UP! Glenview, Ill.: Good Year Books, 1995.

Gardner, Robert, and Eric Kerner. Science Projects about Temperature and Heat. Springfield, N.J.: Enslow, 1994. Jones, Mary, and Geoff Jones. Physics. New York: Cambridge University Press, 1997.

Nye, Bill. Bill Nye the Science Guy's Big Blast 0f Science. Reading, Mass.: Addison-Wesley, 1993.

VanCleave, Janice.janice VanCleave's Guide to the Best Science Fair Projects. New York: Wiley, 1997.

Janice VanCleave's Physics for Every Kid. New York: Wiley, 1991.

Wollard, Kathy. How Come? New York: Workman, 1993.