Oobleck, the friendly quicksand

By Erica Campbell

Almost everyone has seen a TV show or a movie where someone gets trapped in quicksand. Since you are unlikely ever to run into real quicksand, here’s an experiment that you can do safely at home to see and experience how that legendary goop behaves. Making this homemade quicksand, called “oobleck,” can be a great activity for teens to do when they babysit younger kids.

What You need:

• two or more 16-ounce boxes of cornstarch
• water
• measuring cup
• a plastic container about the size and shape of a shoe box
• some newspaper or a drop cloth
• bowls, spoons and a cookie sheet (optional)

What You Do:

1. Pick a large flat space as your work area, and lay down the newspaper or drop cloth.
2. Pour one box of cornstarch into the container.
3. While stirring, slowly pour the water into the cornstarch. You should use up to about a cup of water per box (maybe a little more). The resulting goop should have the consistency of honey; it takes a little practice to get the cornstarch/water ratio just right, so have an extra box of cornstarch so you can make adjustments.

Once your oobleck is made, play with it! Experiment by putting your hand in slowly and trying to pull it out quickly. Trying stirring the oobleck slowly and then quickly. Grab a handful of it and squeeze, then open your hand and watch what happens. Or pour the oobleck onto a cookie sheet and slap it. How does it react?
Engage younger children in a game of quicksand: Drop a plastic toy into the oobleck and see what happens. Then try to rescue the toy using your own invention.
When you are finished, store the oobleck in the plastic container. When you want to use it again, just add some water. When you’re ready to throw it away, dispose of it in the plastic container with the lid on. Do not pour it down the sink; it may clog the pipes!
Sources:

http://www.seed.slb.com/qa2/FAQView.cfm?ID=217

http://en.wikipedia.org/wiki/Non-Newtonian_fluid

Shhh… Oobleck is chemistry—and physics!

Believe it or not, when you make oobleck, you’re doing chemistry! The mixture’s strange behavior is due to the fact that, like quicksand, it is a suspension. When you mix things together, several things can happen. You can make a solution, like Kool-Aid, where one thing (sugar) is dissolved into another (water). You can make a mixture, like salt and pepper, where two things are mixed together but remain individual particles. Or you can make a suspension, where one thing (cornstarch) is evenly distributed into another (water).
Something else fascinating about oobleck is that it is a non-Newtonian fluid. Isaac Newton was one of the key physicists who created laws explaining how the physical world works. According to these laws, liquids behave one way and solids behave another way. Because oobleck doesn’t behave like a liquid or a solid, instead behaving a little like both, it doesn’t follow these laws. For example, when you stir the oobleck slowly, it acts like a liquid, flowing around the spoon. Or if you pour it slowly, it will flow like a liquid. But if you try to stir it quickly, it starts to act like a solid. That is why you can submerge your hand by slowly putting it in the oobleck, but if you slap it quickly, it is like hitting a hard surface.

Erica Campbell is science manager at the Creative Discovery Museum.