Science Investigative Project: Appendix D

Topic of investigation:

Bouncing polymer ball

A – Observations Made

When my sister was bouncing a polymer ball (silly putty), I was curious as to what the ball was made of. I found out that it was made of borax (sodium tetraborate), PVA glue (polyvinyl acetate) and cornstarch. Learning that the reaction between borax and the polymer in glue, PVA, allows the ball to be able to bounce, I decided to test how borax affects the elasticity of the ball.

B – Research Question

Does the amount of borax used affect the height of rebound of the ball?

Does the concentration of borax used affect the height of rebound of the ball?

C – Hypothesis Statement

The greater the amount of borax, the greater the height of rebound of the ball.

The higher the concentration of borax, the greater the height of rebound of the ball.

D – Short summary of research done of the area of investigation

A molecule is two or more atoms bonded together by an exchange or sharing of electrons. Molecules made of long chains of atoms or groups of atoms are called polymers.

Some background research on this topic are that the polymer ball is made from the reaction between glue, which contains the polymer called polyvinyl acetate (PVA), and borax (sodium borate). The covalent bonds along the chain of PVA are strong, but the bonds between chains are weak. By adding borax to PVA, it allows the formation of strong cross-links between chains, forming a stronger and more elastic polymer.

The weak intermolecular bonds that hold the polymer together provide flexibility and rotation about the chain of the cross-linked polymer. Cornstarch helps to bind the molecules together, giving the ball the property of elasticity as it helps to maintain the shape of the ball. This flexibility and elasticity makes the polymer an elastomer, which has elastic properties and will recover its original size and shape after being deformed. Thus, when the polymer hits the ground, it will be able to bounce back up. It is said that cross-linking may increase the strength of the polymer, and since a greater amount and concentration of borax solution used would increase the number of cross-links, it would increase the strength of the polymer, allowing it to bounce higher.

E- Bibliography