STEM Tuesdays: Oobleck!

It’s a liquid! It’s a solid! It’s…oobleck! Let’s learn about this amazing non-Newtonian fluid named after the Seuss book Bartholomew and the Oobleck. So gather the materials below, follow the instructions, and let’s do some science!

Materials & Instructions

2 cups cornstarch
1 cup water
A large bowl
Optional: food coloring

STEP 1. If you have food coloring and want to make your oobleck colorful, go ahead and add a few drops of food coloring to your water now.
STEP 2. Mix your cornstarch and water together. Use some muscle!
STEP 3. Play with your oobleck! What happens if you squeeze it really tightly or slap it? What happens if you let it drip down your fingers or gently rest a hand on top?

What happened?

Oobleck is a non-Newtonian fluid, which means that it changes viscosity, or how it flows, depending on stress. When we apply a lot of force, like quickly balling it up in our hands or hitting the surface, then it acts like a solid. If we allow our hand to gently rest in it or allow the balled up oobleck to drip down our hands, then it acts like a liquid.

Another example of a non-newtonian fluid is ketchup, but ketchup behaves the opposite way. When our ketchup won’t come out of the bottle, what do we do? We apply force by hitting the bottle with our hand, which changes the viscosity of the ketchup so that it squirts out easily.

Vocab Words

Newton: Sir Isaac Newton was a mathematician and scientist born in 1642. The word “Newtonian” is named after him.
Newtonian Fluid: A Newtonian fluid is a fluid where the viscosity, or thickness, does not change, even when force is applied to it. Think about water, milk, or juice.
Non-Newtonian Fluid: A non-Newtonian fluid is a fluid whose viscosity, or thickness, changes when force is applied to it. Oobleck and ketchup are both examples of non-Newtonian fluids.
Viscosity: When we talk about the viscosity of liquids, we’re talking about how thick or thin the liquid is. Thin and thick liquids flow differently. Think about a thin liquid like water. How does water flow over your fingers? Now think about a thick liquid like honey. How does honey flow over your fingers?

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