Bouncy Ball Science
Take me out to the ballgame! March is the time of year when baseball players head to spring training to practice pitching, hitting and fielding. If baseball is not your thing, you can have fun by making up your own type of ball game. In fact, with a bit of science, you can even create your own ball!
borax (you can find borax in the laundry section at your local supermarket)
food coloring (optional)
two plastic or paper cups
a metal spoon or wooden craft stick (to stir your ingredients)
1.) Put two tablespoons of warm water in one of the cups.
2.) Add ½ teaspoon of borax to the water and stir the mixture until it is completely dissolved.
3.) Put one tablespoon of glue in the second cup. (If you want to create a colorful ball, you can add a couple drops of food coloring to the glue.)
4.) Add ½ teaspoon of the borax and water solution to the glue. Do not stir!
5.) Now add one tablespoon of cornstarch to the glue and wait 10 to 15 seconds before stirring everything together.
6.) Keep stirring until the mixture becomes very stiff.
7.) When the mixture becomes impossible to stir, take it out of the cup and knead it with your fingers until it sticks together and becomes elastic. This may take several minutes, so be patient.
8.) Once you have finished kneading, you can roll the dough into a nice round ball. Keep rolling the ball between your hands until it no longer feels sticky.
9.) Drop your ball on a table or clean floor and watch it bounce.
10.) When you are done playing, place your ball into a sealed plastic bag. It should keep for several days.
Now Try This:
Try making another ball but adjust the amount of one of the ingredients. For example, add more cornstarch or borax. How does this affect the bounce of the ball? You can also try making a ball with clear glue or glue gel in place of the white glue.
What’s Going On?
Glue is made up of long chains of molecules, called polymers. When you add borax to the glue, the polymers link together like a net. The cornstarch helps bind the molecules together so that they hold their shape better. If you adjust the amount of some of the ingredients, your mixture will have different properties. Extra cornstarch makes the ball more elastic, while additional glue makes the mixture very slimy.
Debbie DeRoma is the education manager at the Reuben H. Fleet Science Center.
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