What in the World is Oobleck?

oobleckIt’s the gooey, messy, sticky, green substance that fell from the sky in Dr. Seuss’ book Bartholomew and the Oobleck.

In the story, the King of Didd is bored, so he asks his magicians to change the weather and Oobleck fell from the sky, covering the entire kingdom. Eventually, in the world of science, the word Oobleck became synonymous with a substance that pours like a liquid, but when force is added to the substance, like hitting or squeezing with your hands, it becomes solid.

NON-NEWTONIAN FLUID
Sir Isaac Newton’s third law of motion states that for every action in nature there is an equal and opposite reaction. Applying this law, hitting or smacking Oobleck should result in a splash — similar to smacking water in a swimming pool. Amazingly, if you filled a swimming pool with the gooey stuff, you can run across the surface without getting wet. Oobleck does not splash; in fact, it momentarily becomes a solid substance.

Further, it’s an example of a fluid that has changing viscosity (how thick or thin a substance is). Its thickness changes depending on the stress or force applied to it and is considered to be “Non-Newtonian.”

Conversely, when a fluid’s viscosity is constant, it is referred to as a “Newtonian” fluid. Non-Newtonian or Oobleck-like fluids include ketchup and quicksand. Ketchup becomes less viscous when agitated and is easier to pour if you shake first. Also, quicksand gets more viscous when force is applied, so swim slowly to shore when trying to escape quicksand. If not, it will get thicker the more force you use to escape.

CORNSTARCH AND WATER

If you don’t have quicksand nearby, mixing cornstarch and water is the classic experiment to simulate Oobleck goo. Typically, it’s a mixture of 1 cup of water to ½ cup of cornstarch with food coloring added to make for some gooey, sticky fun! You can get hands-on experience with Oobleck’s unusual physical properties by touching, pouring and mixing the cornstarch and water mixture. Luckily, it cleans up easily with water!

 

 

CLASSROOM DISCUSSION

What other non-Newtonian substances can you think of? Is Silly Putty™ non-Newtonian? How about glass?
What would happen if you put Oobleck in the freezer? What if you left it out in the sun?

 

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