Other Ideas

After conducting background research on this topic, I considered also testing how the amount of glue and cornstarch used affects the height of rebound of the ball. This is because they are both important components in making the polymer ball.

I also found out that adding more cornstarch would indeed have an effect on the height of rebound of the ball. More cornstarch would increase the elasticity of the ball by allowing binding the molecules of the polymer more tightly, thus allowing the ball to retain its shape better when it is deformed (e.g. being thrown on the ground). An increased elasticity would increase the energy of the ball when it is released, thus possibly causing an increase in the height of rebound of the ball.

Glue on the other hand, is a flexible polymer that gives the ball its strength, and is also the component that cross-links to itself when reacted with sodium borate. Thus, a greater amount of glue might increase the strength of the ball and may allow it to rebound to a greater height.

However, after more consideration, I realized that the investigation would not be a fair one if I were to test these two variables. This is because when the amount of glue or cornstarch is varied, the difference in the amounts added would be enough to cause the balls to be of different sizes. More than one variable would then be tested at the same time, the amount of glue or cornstarch used, and the size of the ball, making the experiment an unfair one. The results would also be inconclusive as I would be unable to deduce which factor was the one contributing to any differences in the height of rebound of the ball.