Oobleck

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Oobleck
Age Range all ages
Group Size small (1-5), medium (6-20)
Setting outdoors
Setup Time medium (6-30 min)
Duration medium (11-30 min)
Subjects states of matter
Key terms matter, non-newtonian, solid, liquid, suspension
Materials cornstarch, water, plastic tub
Alias obleck, cornstarch and water experiment
Presentation Style interactive, student led

Brief Description

Students will create a non-newtonian liquid from cornstarch and water. Students will be able to play with the "oobleck" and maybe even walk on it!

Objective

to learn about how substances are not necessarily entirely solid or liquid and that some substances can possess properties of both

Scientific Background

Our cornstarch goo (sometimes referred to as “oobleck” from the Dr. Suess book) is what scientists call a “Non-Newtonian” liquid. Basically, Sir Issac Newton stated individual liquids flow at consistent, predictable rates. As you likely discovered, cornstarch goo does NOT follow those rules – it can act almost like a solid, and them flow like a liquid. Technically speaking, the goo is a SUSPENSION, meaning that the grains of starch are not dissolved, they are just suspended and spread out in the water. If you let the goo sit for an while, the cornstarch would settle to the bottom of the bowl.


So why does this concoction act the way it does? Most of it has to do with pressure. The size, shape, and makeup of the cornstarch grains causes the cornstarch to “lock-up” and hold its shape when pressure is applied to it. People have filled small pools with oobleck and they are able to walk across the surface of it (as long as they move quickly.) As soon as they stop walking, they begin to sink.

This Is How You Play

  1. Everyone should roll up their sleeves and prepare for some gooey fun.
  2. Pour box of cornstarch into tub.
  3. Add water a little bit at a time, while stirring the mixture. The secret is to add the water slowly and mix as you add it. When you have about a 2:1 cornstarch to water ratio the mixture will appear to be a liquid but when pressure is applied it will become solid. When pressure is no longer applied it will become a liquid once again.
  4. Play with the oobleck! What is even more fun is trying to walk on the oobleck. Some people have even made their oobleck dance by placing it on a speaker and playing music with a lot of bass.

Variations

Variations for Older Students

  • Start with a game of blob tag, during which the person who is “it” will tag others, who will then link their arms with the tagger until everyone is part of the blob. Talk about the goo, or oobleck, they are about to make and show an example if you have one to demonstrate the consistency of the substance. Give campers bags with a little bit of water in the bottoms and have them pick which color of food coloring to put in the water. When adding cornstarch to the water, be sure that there is between a 1:1 or 1:2 ratio of water to cornstarch. Zip the bags and have campers squish their oobleck together until the ingredients are fully combined. Talk about how oobleck can be hard like a solid when you give it a quick tap, or flow like a liquid if you hold the bag sideways.

Variations for Younger Students

  • see variations for older students ^^


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