Materials

• cornstarch
• water
• food coloring (optional)
• large bowl

Procedure

1. Pour about a cup of the cornstarch in the bowl.  Feel the texture of the cornstarch – it’s a very fine powder.
2. If you want to make colored goo, add some food coloring to your water.  Slowly add water to the cornstarch, mixing it in with your hands as you go.  Start by adding about half a cup of water.
3. You are aiming for a mixture that feels like a liquid when you are stirring it, but feels like a solid when you tap on it.  You have it right if you can squeeze it into a ball, but the goo melts through your fingers when you stop squeezing it!
4. Play around with the goo and see what happens.  (Check out the sources listed below for some great ideas on what to do with your goo.)  Observe what changes occur when you add more cornstarch or more water.

How It Works

The goo acts like a liquid sometimes and a solid sometimes because it is not really either.  Instead, the goo is a suspension, meaning that the very fine grains of cornstarch spread throughout the water and are suspended in the water.  They do not dissolve in the water.  When pressure is applied to the goo, the cornstarch grains are forced closer together and form chains.  The water is trapped between the chains, and the result is goo with a more solid structure.  When the pressure is released, the goo can flow like a liquid again.  The goo is known as a non-Newtonian fluid because Sir Isaac Newton said that viscosity (thickness) of a liquid depends on the liquid’s temperature.  But the viscosity of the goo depends on the force being applied to the goo, not on the goo’s temperature.

Warnings

This one is messy, so be prepared!  Be careful not to get the goo in your eyes, and be sure to wash your hands after handling it.

Don’t put your goo down the garbage disposal unless you add PLENTY of water at the same time.

Sources

https://www.scientificamerican.com/article/oobleck-bring-science-home/

https://www.exploratorium.edu/science_explorer/ooze.html

http://www.instructables.com/id/Oobleck/

https://sciencebob.com/oobleck-the-corn-starch-and-water-experiment/

http://www.kidzone.ws/science/cornstarch.htm

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