Making Non-Newtonian Fluid (Oobleck)

OVERVIEW

Fluids like water are typically hard to hold in your hand. The water would simply flow out between your fingers. The experiment below will show you how to make a fluid that follows a unique set of physical rules! 

Materials

• 1 ½ cups cornstarch
• 1 cup water
• Medium sized bowl
• Food colouring (optional)

Instructions

1. Add the cornstarch to your bowl. Slowly, mix in the water with a spoon or your hands slowly. Break up clumps of cornstarch as much as possible. 
2. Add more water or cornstarch as needed to get the right consistency (creamy, like half-melted ice cream).
3. Once your consistency is correct, try dragging your finger over the surface of the fluid. Note your observations.
4. Try grabbing and holding a fistful of your fluid. Then loosen your grip and open your fist. What happens to the fluid?

How It Works

If your mixture was successful, you will have created a fluid that briefly solidifies when pressure is applied. This is called a Non-Newtonian Fluid because it doesn’t follow the rules Sir Isaac Newton observed in fluids like water hundreds of years ago.

But why does your fluid act this way? The secret is the cornstarch. The small particles in cornstarch can’t dissolve in the amount of water you used (your water is saturated with cornstarch), so the particles stay suspended in the liquid. This might not be a big deal when you move the fluid slowly, but if you act on the fluid quickly and apply more pressure, the cornstarch particles group together. That is why the fluid only seems to solidify if you firmly press on it. 

In theory, you could fill a swimming pool with your creation and run across the surface!