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Oobleck

  • Science
  • Grades 2-3
  • 129 words
  • Also written for younger readers
Paint is a non-Newtonian fluid. In non-Newtonian fluids, viscosity varies with the stress they are exposed to. Paint that is under low stress will behave differently from paint that is under high stress. When a surface with paint turned from horizontal to vertical orientation, it will be exposed to stress from gravitation. Therefore, instead of slipping along the surface, it forms very large drops, that are very dense and almost solid. This creates the great effect that can be seen in the figure.
Paint is a non-Newtonian fluid. In non-Newtonian fluids, viscosity varies with the stress they are exposed to. Paint that is under low stress will behave differently from paint that is under high stress. When a surface with paint turned from horizontal to vertical orientation, it will be exposed to stress from gravitation. Therefore, instead of slipping along the surface, it forms very large drops, that are very dense and almost solid. This creates the great effect that can be seen in the figure. ElisaG87 · cc by 4.0 · source

A non-Newtonian fluid is a thixotropic fluid which changes its viscosity when the forces on it change.

Other flow properties may also be affected. Most commonly viscosity of such fluids is not independent of the shear rate or the shear rate history. Examples of such fluids are blood, quicksand and certain components of cement. Many lubricants, ketchup, and oobleck. Also certain forms of dough and pudding also have this property.

The other kind of fluids that do not show this behavior is called Newtonian fluids.

It is very simple to make a non-Newtonian fluid at home. All one needs is water and cornstarch. Mix these two ingredients together at a rate of one part cornstarch and one and a half parts water. That makes a non-Newtonian fluid called oobleck.

Written for younger readers

Oobleck, in simpler words

This version comes from Wikijunior, a set of books written for children aged 8 to 11. It is shorter and uses plainer language than the article above.

From Wikijunior: Big Book of Fun Science Experiments

Oobleck, Goo or Goop is a strange substance that has some of the properties of a liquid and a solid at the same time. Substances like this are called non-Newtonian fluids, because they do not follow the normal rules of solids and liquids. Newtonian solids, like wood or ice, hold their shape. Newtonian liquids, like oil or water, usually take the shape of the container they are in. Non-Newtonian fluids like Oobleck are sometimes liquids and sometimes solids.

If you have ever melted chocolate without stirring it, you will notice that the squares of chocolate hold their shape until you stir them up. Melted chocolate is also a non-Newtonian fluid.

As with all experiments, you should talk to an adult before trying to make Oobleck. Oobleck is safe to touch; however, it can be very messy. You should wear an apron to keep your clothes clean. If you get Oobleck on your clothes or on the floor, you can easily clean them up with water.

  • Water
  • A cup of cornstarch
  • A bowl
  • A spoon

That’s it, isn’t that easy!

  • Put about a cup of cornstarch into the bowl.
  • Pour about a cup and a half of water into the bowl and stir.

All the cornstarch should be covered in the water. There should be no dry cornstarch visible. If there is dry cornstarch, add a tiny bit more water and stir again. Keep adding a tiny bit of water and stirring until all the cornstarch is covered in water. The mixture should look wet but be difficult to stir, as if you are trying to stir a solid.

Dig in!

Note: If your oobleck starts getting too dry, just add a little more water and stir it again.

Pick up a handful of oobleck and squeeze it in your fist. Does it feel like a solid or liquid?

Now open your hand and hold it over the bowl. What happens? Now is the oobleck a solid or a liquid?

When is the oobleck a solid? When is it a liquid?

Find a small object such as a plastic toy and attempt to float the object on the oobleck. Can you do it?

The cornstarch is suspended in the water as a starch and water mixture. A simplified explanation is: the starch molecules are long chains of atoms. When you let them move slowly, they can slide past each other. When you squeeze or hit them, they become tangled and cannot move.

However, scientists are still investigating strange substances like oobleck. There are still many questions to answer!

Where this page comes from

The article above is adapted from “Oobleck” on Simple English Wikipedia, by its contributors. We removed reference markers, navigation boxes and tables, expanded measurement templates into readable numbers, and kept the prose otherwise intact. The simpler version is adapted from Wikijunior on Wikibooks.

Both sources are published under CC BY-SA 4.0, so this page is published under the same licence. You may share and adapt it, including commercially, as long as you credit the original and keep the same licence.

Worksheets, answer keys and printable layouts elsewhere on K5Print are our own work and are not covered by this licence.