Bouncing Balls

Purpose:

Two solutions are mixed to make a solid. This solid can then be formed into a ball that will bounce very well. The alcohol is used to join the silicon monomers into a polymer.

Materials:

• graduated cylinder (20 ml).

• 20 ml of undiluted sodium silicate solution.

• 5 to 10 ml of 95% ethanol (ethyl alcohol) or in a pinch; isopropyl alcohol. Isopropyl does not work as well as the ethanol.

• rubber gloves.

• popsickle stick.

• paper towel

Procedure:

1. Put on the gloves and apron.
2. Measure out 10 ml of ethanol and put it into a cup. Wash the graduated cylinder and dry it.
3. Measure out 20 ml of sodium silicate solution. Mix the ethanol and sodium silicate solutions together.
4. Stir the solution in a circular motion with the popsickle stick.
5. When the solid forms take it out of the container and form it into a ball by rotating it in your hand.
6. Use the paper towel to catch the excess liquid and dry your gloves.

Discussion:

• Make more Bouncing Balls, but vary the amount of alcohol by 5 ml.
• If stretched slowly, what happens?
• If pulled rapidly apart, what happens?
• If If the ball crumbles you can form it into a new ball by pressing it together between the palms of your hands.
• Keep the ball in a sealed plastic bag or jar.

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