Oobleck Experiment: Is It a Solid or a Liquid? (The Science, Explained)
By Ahmed, founder
Oobleck is a mess in the best way. Mix two kitchen ingredients and you get a goo that you can punch without a splash, then watch ooze through your fingers. Kids love it. It also teaches something real: not everything is simply a solid or a liquid.
Oobleck recipe
You need:
- About 1½ to 2 cups of cornstarch (called corn flour in some countries)
- 1 cup of cold water
- A big bowl or baking dish with sides
- Food colouring, if you like
Pour the cornstarch into the bowl and add the water slowly, mixing with your hand. Stop when it flows like honey when you let it drip, but feels firm when you press quickly. If it’s too runny, add cornstarch. If it’s crumbly, add water, a little at a time.
What to try
Make a small chart. For each test, predict first: “solid” or “liquid”?
- Slap it. It feels hard and doesn’t splash.
- Rest your hand on it. Your fingers sink in slowly.
- Roll a ball. It holds its shape while you roll it, then flows off your palm as soon as you stop.
- Punch it, then pull slowly. A quick tug resists, a slow pull comes away easily.
- Drop a small toy. It lands on top, then sinks.
After the tests, ask: “When did it act like a solid? When did it act like a liquid? What was different?”
The science
Oobleck is a non-Newtonian fluid and, more specifically, a shear-thickening one. Oobleck is a suspension: tiny cornstarch particles floating in water. When you move it slowly, the particles slide past each other with water in between, so it flows. When you hit it or squeeze it hard, the particles get pushed together before the water can move out of the way, and they jam up. For that moment, it resists like a solid. Let go, and the particles spread out again.
Scientists are still studying exactly how particles jam under sudden force, so you can honestly tell your child that this is an area where researchers are still working things out.
So is oobleck a solid or a liquid? It’s best to say it has some properties of each, depending on how fast you push on it. That is a great answer, because it shows children that categories are tools for sorting, and nature doesn’t always fit neatly.
Where else does this happen?
Quicksand behaves a little like this, though it’s a different mix of sand and water. Some body armour and sports padding use materials that stiffen when hit. Ketchup does something related but opposite: it flows more easily when shaken.
Tips and cleanup
- Do it over a tray or outdoors. It’s messy and dusty when dry.
- Don’t pour it down the sink. Cornstarch and water can clog pipes. Scrape it into the trash, or let it dry and brush it into the bin.
- Wash hands afterwards. It also dries skin a little.
- Keep it away from pets and don’t eat it. It isn’t food once it’s been handled.
- Oobleck dries out and goes crumbly overnight. Add a little water to bring it back, or make a fresh batch.
Make it a fair test
Older children can turn it into an experiment. Change one thing, like the ratio of cornstarch to water, or the temperature of the water, and measure how long a marble takes to sink. Repeat each three times. That’s a real investigation.
Our lesson Is oobleck a solid or a liquid? has the steps, the explanation for parents, and ways to make it easier or harder for different ages.
More kitchen science
Oobleck is one of the experiments in Kitchen Chemistry for Families. You’ll also find a homemade lava lamp and a volcano that actually teaches something. More ideas for parents are on our parents page, and you can sign up for three lessons free.