Oobleck

Materials:

* 1/2 cup + 1 teaspoon cornstarch

* 1/4 cup warm tap water

* small plastic or plastic-coated paper bowl

* paper towels or newspapers

* 1 teaspoon measure

* 1/4 cup measuring cup

Procedure

Cover your work area with paper towels or newspapers. Place 1/2 cup cornstarch in your bowl, add 1/4 cup water, and mix with your hands until it all goes together.

Add 1 extra teaspoon of cornstarch and mix until it is smooth again.

Use your fingers to scrape up a handful of oobleck. Hold the oobleck in the palm of your hand. Note what it does.

Put all the oobleck back in the bowl and scrape it together into one clump. Poke the clump with your finger. Does it go in more easily when you poke hard or when you poke gently?

Take some of the oobleck and try to roll it into a ball by rubbing it between your palms in a circular motion. What happens while you move it? What does it do when you stop?

How does the oobleck act when you pull it apart slowly and when you pull it quickly? Close your fist around the oobleck quickly and then close it slowly. When does it act like a liquid? A solid?

How it works

The name that most scientists give to this mixture is non-Newtonian liquid. It has some properties of both the liquid and solid states. It has the unusual property of becoming more like a solid as you put more pressure on it. That is why when you press it into a ball it stays in a ball shape while you roll it, but as soon as you stop, it becomes runny and flows in your hand. The nature of the non-Newtonian liquid is complex. It is an effect of the water, flowing between the cornstarch molecules, which changes when pressure is applied. The pressure drives the liquid water out of the spaces and temporarily solidifies the substance. This effect is the same as in quicksand, where an underground water source provides the water to mix among the sand particles, giving it properties similar to oobleck's.