Take a look at this video to see the impressive effects of
Oobleck is made of ingredients you probably have in your home
already! Cornstarch or cornflour is often used to thicken
sauces, among other things, but when you mix it with water
something amazing happens. It becomes a non-Newtonian
fluid. It is a kind of smart material. When you hit hard it
behaves like a solid. But if you push it slowly it behaves like a
liquid. This is because of the viscosity of the liquid; viscosity
is how well a liquid flows or how resistant it is.
What's going on?
Cornflour is made up of lots of tiny (<0.01mm) starch
particles. These are very attracted to water, so the water gets in
amongst them very quickly.
The water acts as a lubricant, so when you move the cornflour
slowly, the particles have time to move past each other and they
can flow like a liquid.
However, if you apply a rapid force it causes the particles to
move slightly. The particles that are almost touching jam
together and the water that was between them moves sideways
slightly into the gaps. Now instead of having lots of lubricated
individual particles you have a solid structure of lumps touching
each other which can't flow.
Cool stuff isn't it? Take a look at this next experiment
to see how even sound pressure has an effect. Don't try this
one at home without out permission from the parents and a lot of
Making your oobleck dance:
Launch the video in another window.