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.
Understanding Oobleck Non-Newtonian Investigation
Oobleck is best understood as a suspension. A suspension has tiny solid pieces spread through a liquid rather than dissolved into it. Cornstarch does not disappear into the water the way sugar does.
Each grain stays separate, with a thin layer of water around it. This structure explains why the mixture can change its behavior. The important idea is not simply how hard someone pushes.
The speed of the push matters. A quick push gives the water little time to move out of the way.
The grains crowd together and temporarily form a tight network. That network resists movement and can support a hand for a moment.
When the pressure stops, the crowded grains separate again. Water slips through the spaces between them, so the mixture can spread and drip. This change is reversible.
Nothing new is made during the experiment. The cornstarch and water are only rearranging. Students can notice that a ball of oobleck stays together while it is rolled quickly between their hands.
If they stop rolling, the same ball slowly flattens. This is useful evidence because it shows that the material changes with motion, not because it is warming up, drying out, or turning into a different substance.
A fair investigation changes one thing at a time. Students can compare mixtures with a little more water or a little more cornstarch. A wetter mixture usually flows more easily.
A drier mixture may feel firmer and crack more readily. They can test each sample using the same action, such as pressing one finger quickly, pressing one finger slowly, or rolling a small amount for the same length of time. Observations should be specific.
Instead of writing that a sample was weird, students can record whether it spread, held a shape, sank slowly, or resisted a fast tap. Repeating each test helps separate a real pattern from an accidental result.
Similar changing textures appear in everyday materials. Ketchup may resist leaving a bottle until it is shaken. Toothpaste holds its shape on a brush but spreads when pressed.
Some paints become easier to brush when moved, which is the opposite pattern from oobleck. These examples show that fluids do not all have one fixed thickness. When learning this topic, pay attention to particle size, the amount of water, and the speed of movement.
Clean up with a spoon or paper towel and place leftovers in the trash. Oobleck can settle and harden in pipes, so it should not be washed down a sink.
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.