Non-Newtonian Fluids
Non-Newtonian fluids are liquids that get thicker or thinner when you push, stir, or squeeze them.
Cornstarch and water in a bowl behaves like a non-Newtonian fluid. Stir it slowly and it flows like thick soup. Punch it fast and it turns solid under your fist. The faster you push, the thicker it gets.
Explaining non-newtonian fluids by grade level
Mix cornstarch and water in a bowl. Stir it slowly. It flows like a liquid. Now punch it fast. It turns hard like a solid. Pick some up and squeeze. It feels firm in your hand. Open your hand and it melts back to goo.
Projects that explore non-newtonian fluids
Some liquids get thicker when you push them hard. A mix of cornstarch and water acts this way. Squeeze it hard and it forms a solid ball. Let go and it drips through your fingers like honey.
Oobleck thickens under force. Push your hand in slowly and it feels like water. Slap the surface and it turns solid under your palm. This behavior is called shear thickening — the opposite of how quicksand works. Quicksand gets thinner when disturbed. Oobleck gets firmer. Test both fast and slow movements to feel the difference for yourself.