Chemistry Lecture Demos

Corn Starch Stress Balls

Introduction

This is a fun, hands-on activity and great for children to get involved in! This activity involves creating a suspension of corn starch in water. Scientifically, this mixture has the properties of both a solid and a liquid. We call this a non-Newtonian fluid, which means that it does not behave as a typical fluid. The mixture will flow like a liquid, but will break into pieces like a solid. Other examples of non-Newtonian fluids include paint, Silly Putty, PVA slime, or ketchup.

When you observe the corn starch mixture, it appears to be wet, but it will become powdery in texture when you rub it between your fingers. It will withstand a sudden shock, but it will not support the weight of an object laid on its surface (it acts like quicksand). This is due to its characteristic as a dilatant – under stress, the mixture will dilate, or expand. The viscosity of the cornstarch water mixture will increase when stress is applied.

In this demonstration, a corn starch and water mixture is created and put into a latex balloon, sealed, and the participant can take home their very own, self-made stress ball.

Materials

  • large wide container, aluminum cooking tin, or aluminum pie pan
  • corn starch
  • water
  • plastic spoon
  • scissors
  • latex balloons
  • wide stem funnel (you can make your own funnels by cutting the top off of a 16-oz soda bottle)
  • plastic drinking straw
  • tarp or plastic (to facilitate easy cleanup) (optional)

Procedure

  1. Cover your table with the tarp or plastic and put the large container or aluminum cooking tins on the table.

  2. Start with 2 cups of corn starch in your container. Slowly add water and use your fingers to mix until a gooey, fluid-like consistency is obtained. This fluid should drip slowly from your hand. If you strike it with a hard blow, it will not splatter – an indication that you added to much water. If you add too much water, add more corn starch until the correct consistency is obtained.

  3. Once the desired consistency is reached, place the funnel into the opening of a latex balloon. A plastic drinking straw inserted into the balloon next to the funnel to provide an escape route for any air still inside the balloon, which makes filling easier.

  4. Drip the corn starch / water mixture into the funnel until the balloon reaches the desired size of your stress ball. Then, remove the funnel and straw and tie a knot in the balloon.

Safety

There are no special safety precautions. All ingredients are safe for all ages (unless a participant has a latex allergy). It can be messy, so participants may want to wear gloves and/or lab coats or aprons.

Disposal of Waste Products

The corn starch / water mixture can be safely washed with water and flushed down the drain.

Making Stress Balls at Fun Fest
Making Stress Balls at the Fall Fun Fest in Cookeville.

 

 

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