How Does Temperature Affect the Stretch of Rubber Bands?

Research Questions:

• What happens to rubber when it is heated?
• What happens when it is cooled?

Entropy, a measurement of the orderliness of the molecules that make up a substance, determines whether a material expands or contracts when it's heated. Let's find out what happens to a rubber band when it is both heated and cooled.

Materials:

• Rubber band
• Scissors
• Weight set or washers
• Shoebox (about the length of a ruler)
• Ruler
• Pencil
• Refrigerator
• Hair dryer
• Pen
• Lab notebook

Experimental Procedure:

1. Cut your rubber band in half with the scissors.
2. Tie a weight or washer to one end.
3. Sit the shoebox so that it stands tall and place the ruler inside. Poke a hole into the middle of the top of the box. Thread the rubber band through the hole.
4. Tie the rubber band to a pencil. Be sure to make sure the weight tied to the other end can swing freely.
5. Allow the rubber band to stretch for three minutes at room temperature. Then measure the length of the rubber band with the ruler. Record your data in your notebook.
6. Now put the shoebox into the refrigerator for 15 minutes. After 15 minutes, remove the shoebox, and measure the length of the rubber band again. How does the rubber band feel now? Record your data and observations.
7. Now it's time to heat things up! Use a hair dryer to heat the rubber band for 5 minutes. After 5 minutes, measure the rubber band again. How does the rubber band feel now? Record your information.
8. Analyze your data. When did your rubber band have the most stretch? When did your rubber band have the least amount of stretch? Why do you think this happened? Were you surprised? Record your conclusions.

Terms/Concepts: entropy; molecules; expansion; contraction

References:

• Prize Winning Science Fair Projects for Curios Kids, by Joe Rhatigan and Rain Newcomb (Lark Books, 2004).
• "Effect of Temperature on Elasticity of Rubber Bands," Science Buddies