Bouncy Balls

Concept: Polymers
Polymers are molecules made up of repeating chemical units that are strung together to form long chains. When cross-links are formed in a polymer, its chains of molecules are connected in several places, producing a stronger and more elastic polymer. Polymers are stretchable, pliable, and flexible.

Read Aloud: Cool Chemistry Concoctions by Joe Rhatigan

Ingredients:

      ·         2 tbl. Water (Warm)

      ·         ½ tsp. Borax

      ·         1 tbl. Elmer's Glue

      ·         1 tbl. Cornstarch

      ·         Food Coloring

      ·         Plastic Cups

Demonstration:

      ·         Label one plastic cup “Borax Solution” and the other plastic cup “Ball Mixture.”

      ·         In the cup labeled “Borax Solution,” add 2 tablespoons of warm water and ½ teaspoon of borax.
      ·         Stir until the borax is dissolved.

      ·         Add 2-3 drops of food coloring.

      ·         In the cup labeled “Ball Mixture,” add 1 tablespoon of Elmer’s glue, 1 tablespoon of cornstarch and ½ teaspoon of the borax solution. Do not stir. Allow the ingredients to interact for 10-15 seconds and then stir them together until they are well combined.

      ·         When the mixture becomes impossible to stir, take it out of the cup and quickly start molding it into a ball.

      ·         Knead the ball until it is no longer sticky and is solid enough to bounce.

Experiment:

·         What happens when the ratio between the amounts of glue, cornstarch and borax is changed?

·         Does altering the composition of the ball affect its bounciness?

Observations:
The glue is a liquid polymer. This means that the tiny molecules in the glue are in strands like a chain. When the borax is added, the borax acts as a cross-linker that connects all the polymer strands together more tightly.