I first heard about non-Newtonian fluids on an old episode of MythBusters. Anyone remember that show? I used to love it, they always built the coolest contraptions and tested really interesting things. In the episode in question they mixed a bunch of cornstarch into a large tub of water and came up with a “liquid” that you could run across. Ever since then I wanted to try making it myself.
Non-Newtonian fluids are fluids that don’t follow Newton’s law of viscosity. I’ll let you read about that yourself 🙂 The cornstarch and water mixture is probably the easiest non-Newtonian fluid to make and it’s non-toxic and safe for kids to play with. This mixture is commonly referred to as “oobleck”. A name which comes from “Bartholomew and the Oobleck” by Dr. Seuss.
- Dish or bowl (we used a pie plate)
- Spoon or craft stick
The amount of corn starch and water, and the size of the dish will depend on how much oobleck you want to make. The ratio of cornstarch to water is 2:1, so approximately 2 cups of corn starch for 1 cup of water. You may want to experiment a bit with your mixture until you get the right consistency.
- Pour water into bowl/dish
- Add cornstarch
- Stir the cornstarch into the water with the spoon/craft stick
As you stir and the cornstarch begins to mix with the water the mixture should become hard to stir. You should begin to notice that the slower you stir, the easier it will be. If you try to stir quickly it will become more difficult.
Once the mixture is combined have your kids stick their hands in the bowl and play with it. Try things like tapping on the mixture and then slowly putting their hand in and see if they notice the difference. When tapping on or slapping the top of the mixture it should feel hard. When they put their hand in slowly it should be soft and gooey. You can also try rolling the mix in your hands to create a ball. As long as you keep rolling it the mix will stay together and feel hard. Once you stop it will start to separate and drip from your hands. This stuff is a lot of fun to play with!
Most fluids don’t change consistency no matter what you do with them. Their viscosity (how sticky or smooth they are) stay the same whether you pour them, stir them or push them. Non-Newtonian fluids act differently. Yogurt, for example, is generally fairly think and if you try to pour it will come out quite slowly. If you shake a tub of yogurt first it will become less “sticky” and will pour out more quickly. This is an example of a common non-Newtonian fluid.
Oobleck is a non-Newtonian fluid that acts in the opposite way. When cornstarch and water are mixed the starch grains are suspended in the liquid. If you apply pressure to the liquid the cornstarch compresses together and traps the water molecules in between making it behave more like a solid. As soon as the pressure is removed it returns back to its liquid state.