Friday, February 28, 2014

How to Make Your Own Oobleck

Have you ever read Bartholomew and the Oobleck by Dr. Seuss?

It's a story of where an ooey-gooey, green oobleck was not exactly what the king had in mind when he ordered something extra-special from his royal magicians.

Recipe for Oobleck
1/2 cup + 1 teaspoon cornstarch
1/4 cup warm tap water
green food coloring

Mix 1/2 cup of cornstarch and 1/4 cup water and green food coloring in a bowl until it all goes together (you may need to use your hands).  
Add 1 extra teaspoon of cornstarch and mix until it is smooth again.


What's the science going on here?
The name that most scientists give to this mixture is non-Newtonian liquid.  It has some properties of both the solid and liquid 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 over your hand.  The nature of the non-Newtonian liquid is complex.  It is an effect of the water, flowing between the corn starch 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.

CLEAN UP!
Put any Oobleck into the garbage can.  Caution: Do not put the Oobleck in the sink.  It can plug drains.  Roll up and toss in trash.  Wash all containers and desk tops with soap and water.

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