If you’ve ever wondered why it might be hard to get out of quicksand, it’s because it can act like both a liquid and a solid. Cornstarch slime is a fun substance that does this too! When a substance like this has properties of both liquids and solids, they are called non-Newtonian fluids, which you’ll learn more about in this experiment. You’ll also explore what interactions make it go from one state to another. When you slowly press your fingers into cornstarch slime —stored in a Ziploc bag —it’ll feel like a liquid. But when you quickly press your fingers into it, it becomes as hard as a rock! Why do you think that is?
Add a few drops of food coloring to the water until you get a color you like.
Pour a cup of water into the bag (avoid filling the bag more than halfway) and mix with the cornstarch until it’s the consistency of runny cake batter. (If it’s too thick, add an additional tablespoon of water.)
With both hands, apply pressure quickly and feel how the cornstarch slime becomes firm and solid.
Release it and feel the mixture become runny once again in the bag. Experiment with the speed at which pressure is applied. Poke it fast and poke it slow. You just made a non-Newtonian fluid!
We all know that certain substances change from solids to liquids to gases with temperature: water freezes to become ice or boils to become steam. But for non-Newtonian fluids, this change happens based on pressure instead of temperature. If you push down slowly with your fingers, the substance stays liquid, making a well around your fingers. If you push down quickly, it becomes firm beneath your fingers. If you had a life-size tub of cornstarch slime, how would you run across it? With fast stomps or slow steps?
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