Oobleck - Experiment 18

Many of the materials we use every day, like starch, are made up of molecules called POLYMERS. POLY means “many” and MER means “unit”. Because the units of chains are so long, the movement of polymers is restricted. Viscosity is a physical property of liquids that describes their rate of flow. Honey and corn syrup are described as having high viscosity because they flow more slowly than water.

Materials Substitutions
1 500 mL beaker 1 bowl
1 cup cornstarch (1/2 box)
a spatula a spoon
1 aluminum pie pan
scissors
water

Procedure

  1. Pour 1 cup of cornstarch into a bowl or beaker.
  2. Continue to add a small amount of water until the solution begins to thicken. Stir carefully! Do not fight the viscosity of the polymer.
  3. Pour some of the polymer into the pie pan. Try to cut it with the scissors as you pour. Tap the polymer in the pie pan with your hands. Pour some of the polymer into your hands and roll it into a ball. Does the ball retain its shape? Form a long rope (snake) with the polymer and pull it apart quickly. What happens? With your spoon, attempt to draw in the polymer. Can you write your name?

Extensions
Try making one of the other non-Newtonian fluids in this lab manual. See Experiments 19 and 20.

Teacher’s Notes

  1. The Oobleck is a non-Newtonian fluid. A non-Newtonian fluid has properties of both a solid and a liquid, and it reacts to stress with increased viscosity.
  2. The Oobleck can make a mess!! Be prepared for your students to have some “play” time. Towels and water should be on hand.
  3. If you are doing this for elementary age students, you may want to add a drop or two of food coloring. Then you can read Dr. Suess’ “Bartholomew and the Oobleck”.
  4. The mixture of cornstarch and water can be considered a colloidal suspension. A colloidal suspension is a two-phase system in which the starch is not fully dissolved in water but simply MIXED into a permanent suspension that will not settle upon standing.
  5. Other examples of colloids are: fog, whipped cream, foams, jello, and styling gels.

Disposal
The Oobleck can be spread onto a cookie sheet, dehydrated, and reused!!