Discover non-newtonian fluids (substances that act as both a liquid and a solid) and liquids that glow under black light with this messy, but delightful activity!
Have you ever hit some water with a hammer? We’re not sure why you would have, but if you can imagine doing that, you can also imagine that the hammer would make a splash as it goes right into the water. The water doesn’t really push back on the hammer. But what if it did? What if you hit the water, and it stopped the hammer?
The mixture you’re going to make in this activity does just that. Oobleck is a type of mixture called a non-Newtonian fluid. If you push hard on it (no need to use hammers for this part), it hardens up and pushes back against you. If you push lightly on the oobleck, though, it stays liquidy and your hand will easily go into it.
How we did it:
- tonic water - containing quinine
- small container
- black light
Gather your materials!
Add two parts cornstarch and one part tonic water in a small container.
Mix well. This creates a substance that acts as both a liquid or solid - called a non-newtonian fluid! When you press on it, it should feel hard, but when you let go, it should turn back into a liquid.
If the consistency is too watery, try adding a little extra cornstarch. If it’s too dry, add a little tonic water.
Plug in and turn on your blacklight.
Pour the oobleck into your hands and begin playing with it under the blacklight! What happens when you squeeze it?
Oobleck is called a non-Newtonian fluid because it can change its viscosity. Viscosity is a property of liquids that says how fast they flow or how much they resist their shape changing — kind of like how thick a fluid is. Isaac Newton wrote a law a long time ago that said a liquid’s viscosity was supposed to be a constant (unless you change its temperature). Because he never tried making oobleck, he didn’t know that a changing viscosity was possible!
You can test out viscosity at home by trying to stir different liquids. If it’s tough to stir, it has a high viscosity. If it’s easy to stir, it has a low viscosity. And if its viscosity changes and it gets harder (or easier) to stir, then you’ve found another non-Newtonian fluid!