How to Make a Bouncing Polymer Ball

Materials

Before you make bouncing polymer balls, you will need to gather a few materials:

• Borax (found in the laundry section of the store)
• Cornstarch (found in the baking section of the store)
• White glue (e.g., Elmer's glue, which makes an opaque ball) or blue or clear school glue (which makes a translucent ball)
• Warm water
• Food coloring (optional)
• Measuring spoons
• Spoon or craft stick (to stir the mixture)
• 2 small plastic cups or other containers (for mixing)
• Marking pen
• Metric ruler
• Zip-top plastic baggie

Procedure

To make bouncing polymer balls, follow these steps:

1. Label one cup "Borax Solution" and the other "Ball Mixture."
2. Pour 2 tablespoons of warm water and 1/2 teaspoon of borax powder into the cup labeled "Borax Solution." Stir the mixture to dissolve the borax. Add food coloring if desired.
3. Pour 1 tablespoon of glue into the cup labeled "Ball Mixture." Add 1/2 teaspoon of the borax solution you just made and 1 tablespoon of cornstarch. Do not stir. Allow the ingredients to interact on their own for 10-15 seconds and then stir them together to fully mix. Once the mixture becomes impossible to stir, take it out of the cup and start molding the ball with your hands.
4. The ball will start out sticky and messy but will solidify as you knead it.
5. Once the ball is less sticky, go ahead and bounce it.
6. You can store your plastic ball in a sealed bag when you're finished playing with it.
7. Don't eat the materials used to make the ball or the ball itself. Wash your work area, utensils, and hands after you have completed this activity.

Things to Try With Bouncing Polymer Balls

When you use the scientific method, you make observations before experimenting and testing a hypothesis. You've followed a procedure to make a bouncing ball. Now you can vary the procedure and use your observations to make predictions about the effect of the changes.

• Observations you can make and then compare as you change the composition of the ball include the diameter of the finished ball, how sticky it is, how long it takes the material to solidify into a ball, and how high it bounces.
• Experiment with the ratio between the amounts of glue, cornstarch, and borax. Adding more cornstarch will make a ball that stretches and bends. Using less borax will produce a "goopier" ball, while adding more glue will result in a slimier ball.

This activity is adapted from the American Chemical Society's "Meg A. Mole's Bouncing Ball," a featured project for National Chemistry Week 2005.