Oobleck is a squishy, drippy mixture made from cornstarch and water. It is fun for school projects because it can feel like a solid and a liquid in the same experiment. When you squeeze it or hit it quickly, it gets firm.
When you let it rest in your hand, it flows through your fingers like goo.
Key Facts
- Basic recipe: 2 parts cornstarch + 1 part water.
- Squeeze or punch fast: oobleck acts more like a solid.
- Pour or move slowly: oobleck acts more like a liquid.
- Oobleck is a non-Newtonian fluid because its thickness changes when force is applied.
- Fast force pushes cornstarch grains together, making the mixture feel firm.
- Slow motion lets water move between the grains, so the oobleck flows.
Vocabulary
- Oobleck
- Oobleck is a mixture of cornstarch and water that can act like both a solid and a liquid.
- Non-Newtonian fluid
- A non-Newtonian fluid is a fluid whose thickness changes when it is pushed, stirred, squeezed, or hit.
- Solid
- A solid keeps its shape unless a force changes it.
- Liquid
- A liquid flows and takes the shape of its container.
- Force
- A force is a push or pull that can change how something moves or feels.
Common Mistakes to Avoid
- Adding too much water, because watery oobleck will not firm up well when squeezed. Add more cornstarch a spoonful at a time until it feels thick and gooey.
- Testing only slow movements, because oobleck needs a fast push or squeeze to show its solid-like behavior. Try both a quick tap and a slow finger dip.
- Calling oobleck only a solid or only a liquid, because it can behave like both depending on how you touch it. Describe what it does during each test.
- Pouring oobleck down the sink, because it can clog pipes as the cornstarch settles. Throw it in the trash or compost if allowed by your teacher.
Practice Questions
- 1 You mix 2 cups of cornstarch with 1 cup of water. How many cups of mixture ingredients did you use in all?
- 2 A class needs twice as much oobleck. If the recipe uses 2 cups cornstarch and 1 cup water, how many cups of cornstarch and water are needed for the bigger batch?
- 3 A student slowly presses one finger into oobleck, then quickly slaps the surface with a flat hand. Explain why the two tests feel different.