Mix a cup of cornstarch and around half a cup of water together for instant Halloween fun! Cornstarch and water mix together to form a strange concoction, called a shear-thickening fluid, that behaves like a solid when you agitate it, but behaves like a liquid when you let it sit still.
To make your Goblin Goo more Halloween-y, add a drop of food coloring, but you’ll risk staining hands and other surfaces. You can experiment with adding more water or cornstarch to get your goo to the consistency of thick syrup.
The molecules in your mixture are sort of like long ropes. When you leave them alone, or move them slowly, they can slide past each other. However, if you squeeze them, stir them or roll them around in your hands, the ropey molecules look and feel more like a solid. Materials like cornstarch goo are known as non-Newtonian fluids, since they don’t have the normal properties of either a liquid or a solid.
Here’s a “watch and do” video for kids: