Oobleck is a simple classroom project made by mixing cornstarch and water into a strange, squishy material. It feels like a liquid when you let it drip, but it can feel like a solid when you press or hit it quickly. This makes it a fun way to explore how materials can behave in surprising ways.
It is safe, inexpensive, and easy to test with your hands, a spoon, or a small cup.
Key Facts
- Basic recipe: about 2 parts cornstarch to 1 part water by volume.
- Oobleck is a non-Newtonian fluid because its viscosity changes when force is applied.
- Pressing quickly makes oobleck act more solid because the cornstarch particles jam together.
- Moving slowly lets oobleck flow because the particles have time to slide past each other.
- Viscosity means resistance to flow, so honey has higher viscosity than water.
- Ratio example: 1 cup water needs about 2 cups cornstarch for a good oobleck mixture.
Vocabulary
- Oobleck
- Oobleck is a mixture of cornstarch and water that can act like both a liquid and a solid.
- Non-Newtonian fluid
- A non-Newtonian fluid is a fluid whose thickness or flow behavior changes when force is applied.
- Viscosity
- Viscosity is a measure of how strongly a fluid resists flowing.
- Mixture
- A mixture is a combination of substances that are physically combined but not chemically changed into a new substance.
- Force
- Force is a push or pull that can change how an object or material moves or behaves.
Common Mistakes to Avoid
- Adding too much water at once makes the oobleck runny and hard to fix. Add water slowly and stir after each small splash.
- Thinking oobleck is always a solid is wrong because it flows when it is handled gently. Test it by slowly pouring it from one hand to the other.
- Thinking oobleck is always a liquid is wrong because fast pressure can make it resist motion. Try tapping it quickly and then pressing slowly to compare.
- Pouring oobleck down the sink can clog pipes because cornstarch can settle and harden. Let it dry and throw it in the trash instead.
Practice Questions
- 1 A recipe uses 2 cups of cornstarch for every 1 cup of water. How many cups of cornstarch are needed for 3 cups of water?
- 2 A group has 6 cups of cornstarch and wants to use the 2:1 cornstarch-to-water ratio. How many cups of water should they add?
- 3 Explain why a finger poked quickly into oobleck may stop suddenly, while a finger pushed slowly can sink in.