How to Make Oobleck: Is it a Liquid or Solid?

Hypothesis

The hypothesis is that when you mix cornstarch and water, it will create a substance that behaves like a liquid at times and a solid in other times.

Overview

Oobleck is a gooey green substance from Dr. Seuss' book "Bartholomew and the Oobleck". You can make homemade Oobleck slime with our easy Oobleck recipe! Get ready to have so much fun with Oobleck, a weird substance made of cornstarch and water that can act like a liquid and in the next moment act like a solid! When you push or squeeze it, Oobleck behaves like a solid, but when you let it rest, it flows like a liquid. Scientists call it a non-Newtonian fluid, and it behaves in ways that defy our expectations of how liquids should act. It's a great science experiment for all ages, as young kids love this awesome sensory activity, while even university researchers are studying the complex science behind it!

Scientific Terms

non-Newtonian fluid, liquid, solid, viscosity, resistance to flow, shearing force.

Materials

1 cup cornstarch (alternatives: arrowroot flour, potato starch, tapioca flour)
1/2 cup water
a few drops of food coloring (optional)
measuring cup
a spoon
a large bowl or pan - large enough for mixing the Oobleck ingredients and for playing in it.
an airtight container or ziploc bag - The plastic container or bag needs to be airtight to prevent the Oobleck's moisture from evaporating. If an airtight container is used, it can also be used as the play container the next day.
newspaper - Making Oobleck is messy, so it's best to cover your work area!

Procedure

Safety:

The ingredients are non-hazardous, so it is safe to handle with bare hands.

Cover work area with newspapers.
Measure 1 cup of cornstarch into the large bowl.
Measure 3/4 cup water and add in a few drops of food coloring and mix. If you want to make green oobleck as in the story, add green food coloring.
Stir the cornstarch and water together until it reaches the right consistency like honey. If you tap it with the spoon, it should not splash. It may be hard to mix, but take your time to dissolve the cornstarch powder into the water as it can take several minutes. If it's too thin, add more cornstarch. Add more green food coloring until it matches the color in the story.
Play around with it to see how it behaves. You can try picking it up and squeezing it to make a ball, tapping it slowly or quickly with a spoon, and letting it drip through your fingers. You might be surprised by what you discover!
The cornstarch water mixture can be cleaned up with a wet sponge.
Once you're finished playing with Oobleck for the day, store it in an airtight container or ziploc bag in the fridge. It can last for another day of play! If the cornstarch has separated out the next day, simply mix it in the bag by squeezing it a few times or stir it in the container. If it has become too thick, you can add a bit more water.
When you're ready to throw the Oobleck out, there's one more activity that can be done! Check out the 3rd reference and 2nd video on a dinosaur excavation activity below. Be sure to throw it in the trash can and not down the sink, as it can clog the drain.

Results

When you squeeze the Oobleck slime hard or roll it fast, it can form a ball, but when you let go of it, it flows off your hand. When you punch down fast on the Oobleck, it doesn't splash, but when you move your hand slowly through the Oobleck, it feels like a liquid!

Conclusion

Oobleck is a fascinating non-Newtonian fluid that challenges our understanding of how liquids behave, as it can also have properties of a solid depending how it is handled. When there is more pressure on Oobleck, it acts as a solid. When there is no pressure or very little pressure on it, it acts as a liquid.

Oobleck FAQ

What is a substitute for cornstarch in Oobleck?

Cornstarch, arrowroot flour, potato starch, and tapioca flour can form non-Newtonian fluids due to their high concentration of starches. You can use the same Oobleck recipe for the other flours and starches and adjust the amount of water until the right consistency has been reached.

Can you use all-purpose flour/ wheat flour to make Oobleck?

No. All-purpose and wheat flour have a lower concentration of starch than cornstarch, so they don't form non-Newtonian fluids.

Can you use baking soda to make Oobleck?

No. Baking soda does not have any starch in it, so it will not form a non-Newtonian fluid when mixed with water.

What's the science behind Oobleck?

Oobleck is a mixture of tiny cornstarch particles suspended in water. It has some weird properties. When squeezed, it acts like a solid, but when left alone, it drips like a liquid. This is because Oobleck is a non-Newtonian fluid, which means it doesn't behave like typical liquids such as water, which move out of the way when you touch them. Other examples of non-Newtonian fluids include ketchup and quicksand. When a non-Newtonian fluid is exposed to a shearing force, like squeezing or stirring quickly, its viscosity, or resistance to flow, increases. This causes the fluid to act like a solid, depending on the amount of force applied. The strange behavior of non-Newtonian fluids makes them interesting to study and fun to play with.

Is Oobleck edible?

No. Since Oobleck contains raw cornstarch, one should not eat Oobleck. After adding food coloring and handling with your hands, it is not advisable to use Oobleck for cooking.

What are some other uses of Oobleck?

Check out the references and videos on how to use Oobleck in an excavation activity! It's also a great way to dry out the cornstarch so that it'll be easier to throw in the trash.

Also consider

Try adding different amounts of cornstarch and water to see how it affects the behavior of the Oobleck.
Make Oobleck with arrowroot flour or potato starch instead of cornstarch.
Add other materials to the Oobleck, like sand or glitter, to see how it affects its properties.

References

Outrageous Ooze from The Exploratorium
Oobleck: Homemade Slime from The Children's Museum of Sonoma County
Oobleck Dig Site from the University of Alaska Fairbanks - When you're done playing with oobleck, turn it into an excavation activity!

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