January 2015

Oobleck (1/7/15)

MATERIALS:

  • Box of cornstarch (16 oz.)
  • Pitcher of water
  • Large mixing bowl
  • Zipper-lock bag
  • Food coloring (optional)

INSTRUCTIONS:

  1. Pour ¼ of the box of cornstarch into the mixing bowl.
  2. If you want to make the oobleck your favorite color, you can add food coloring into the water pitcher. Slowly pour ½ cup of water into the mixing bowl. Stir the mixture, and don’t be afraid to use your hands!
  3. Keep adding cornstarch and water in tiny amounts until you get a mixture that has the same consistency as honey. For the best results, you will want to mix 10 parts cornstarch to 1 part water – that’s one box of cornstarch to 1-2 cups of water.
  4. Submerge your hand into the bowl of oobleck, and notice its strange consistency. Is your oobleck a liquid or a solid? It’s hard to decide! Sink your entire hand into the oobleck, and try to lift it up very quickly. The faster you move your hand, the harder it is to move. This is what it feels like to be trapped in quicksand!
  5. When you are finished, pour the oobleck into a zipper-lock bag for later use. IMPORTANT: Remember not to pour your oobleck down the drain, it can clog the pipes and stop up the drain. Be sure to dispose of your oobleck in the garbage in its zipper-lock bag!

HOW DOES IT WORK?

The cornstarch and water mixture acts like a solid sometimes and a liquid at other times. All fluids have a property known as viscosity. When we use the word viscosity, we are talking about the thickness of a fluid or its resistance to flow. Have you ever gone to a restaurant that has ketchup in a glass bottle? Sometimes the ketchup can be really hard to get out of the bottle, so we say that ketchup has a high resistance to flow. On the other hand, it is really easy to pour a glass of water, so we say that water has a low resistance to flow.

There are two types of fluids, Newtonian and non-Newtonian. Newtonian fluids have the same thickness no matter how much force you apply to them. Non-Newtonian fluids are the rule-breakers, because their viscosity depends on how much force you apply to the fluid. Some examples of non-Newtonian fluids are oobleck, ketchup, quicksand, shampoo, toothpaste, and blood.