Non-Newtonian Fluid Experiment

It’s Alive!

Cornstarch and Water on a Speaker

This is a fun experiment for all ages. We first did it when my kids were 3 & 6 years old! We love science and STEM activities and this was one of our favorite science experiments. We loved how the cornstarch mixture became a solid and a liquid at the same time. This classic oobleck science experiment is always a hit for kids, and makes the perfect quick science experiment!

What does non-Newtonian mean?

All fluids have a property known as viscosity that describes how the fluid flows – commonly thought of as how thick or thin a fluid is. For instance, honey is much more viscous than water. When a fluid’s viscosity is constant, it is referred to as a Newtonian fluid. Oobleck is an example of a fluid whose viscosity is not constant; it’s viscosity changes depending on the stress or forces applied to it. If you poke it with your finger and apply a large force, it becomes very viscous and stays in place. If you gently pour it, applying little force, it will flow like water. This kind of fluid is called a dilatant material or a shear thickening fluid. It becomes more viscous when agitated or compressed.

Another non-Newtonian liquid is ketchup. Ketchup behaves in the opposite way from Oobleck. You could even call it the “anti-Oobleck.” It becomes less viscous when agitated. Liquids like this are called shear thinning liquids. If you leave a bottle of Ketchup on a shelf, it becomes thicker or more viscous.

You’ll love how much fun it is to do with kids, and kids will love how messy it is. Since the experiment is messy, it’s best to do it outside, or use a drop cloth like we did.

Oobleck, Slime & Dancing Spaghetti: Twenty terrific at-home science experiments inspired by favorite children’s books by Jennifer Williams, ages 4–8

The Scientific Method for Kids

Science is a logical system for exploring our world. Each science experiment should include:

  • Question: Kids should start every science experiment with a question, even if that question is just “what will happen?”
  • Experiment: This is where the fun part comes into play. Test the hypothesis to determine if it answers the question fully.
  • Recording and Analysis: As the test is completed, record what happened. Why did that happen?
  • Retest: Try different variables and try a new test to see if the original answer is confirmed or disproved. Every variable should be tested more than once.

Cornstarch Experiment Explanation

Cornstarch and water mixed acts both like a solid and a liquid. Cornstarch and water is a suspension mixture with a solid dispersed into a liquid. When you press the mixture quickly, the starch molecules close together.

This causes the water to get trapped between the starch chains and create a semi-rigid structure. When you press slowly, this starch chain “block” doesn’t happen and the mixture flows like a liquid.

Because the viscosity of the mixture changes with force rather than heat, the cornstarch mixture is known as a non-Newtonian fluid. Slime is another fun non-Newtonian fluid. Another favorite!


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How to Make Your Non-Newtonian Fluid with Cornstarch

  1. Mix the corn starch and the water together at a ratio of about 10 parts starch to 1 part water.
  2. Start the mixture by adding about ½ of a cup of cornstarch to about 1 cup of water.
  3. Play with the mixture until it reaches the consistency that you want. You’re aiming for a texture that is runny when relaxed, but still firm enough to seize up when they hit the mixture.

Watch Our Video Experiment

What’s Happening

The corn starch mixture (oobleck) will be moved about as the speaker vibrates. Some parts of the speaker will vibrate much less than others (may even be stationary) and the particles which land there will stay there, once they have landed. So you get a build up of particles in the so-called nodes (where there is node displacement) and very few particles in the antinodes because they are constantly being kicked into motion. So, you can see the pattern of the standing waves on the speaker.
It’s a bit like the effect on a windy day, when leaves and rubbish find themselves in sheltered spots and are constantly being removed from the middle of the road, where the wind is strongest.
A ‘good’ loudspeaker unit should not have resonances and should, ideally, move backwards and forwards like an ideal piston – that’s why they are made with a conical shape which gives them strength even though they are very light.

More to explore

What is Jell-O?” from Scientific American
Ask the Experts: What Is Quicksand?” from Scientific American
States of Matter” overview from Idaho Public Television’s Dialogue for Kids
Slime and Goo activities from the American Chemical Society’s Science for Kids
Oobleck, Slime & Dancing Spaghetti: Twenty terrific at-home science experiments inspired by favorite children’s books by Jennifer Williams, ages 4–8
The Everything Kids’ Easy Science Experiments Book: Explore the world of science through quick and easy experiments! By J. Elizabeth Mills, ages 9–12

Digging Deeper

In addition to being a non-Newtonian fluid, Oobleck can be called a heterogeneous mixture. Usually one of two things happen when you mix a solid and a liquid: the solid either dissolves or it separates from the liquid. You have seen this before. For example, if you mix salt with water the salt disappears—it completely dissolves such that the water and salt can no longer be separated. Such a mixture is called a homogeneous mixture, or solution. In contrast, heterogeneous mixtures are not uniform in composition. If you mix particles larger than 1μm, such as sand with water the sand does not dissolve. After you stop mixing the sand eventually settles to the bottom of the container—it separates from the liquid. A heterogeneous mixture with suspended particles large enough to settle down to the bottom of the container upon standing (usually >1μm) is called a suspension. In the cornstarch-water mixture individual tiny particles of cornstarch are suspended throughout the water. The cornstarch pieces are very tiny, with an average size of 1500 nanometers in diameter. (A nanometer is very small — a human hair is about 100,000 nanometers wide!) In Oobleck, the cornstarch pieces are evenly spread throughout the water. These particles are so small that you cannot see them with the naked eye. Suspensions with dispersed particles smaller than 1μm are called a colloid, which means that the particles are so small that they cannot be separated from the mixture anymore. They won’t settle upon standing and can’t be filtered out. Although a colloid looks like the liquid is all one thing, you can see under a microscope that it is actually a mixture of particles suspended in a liquid.

Having the right particle size is important for making a colloid. If smaller particles are used, they will dissolve in the water and not be visible, even with a microscope. For example, think of how sugar dissolves in water, making a homogenous solution. On the other hand, if larger particles are used, such as grains of sand, they will not dissolve in the water. Instead, they separate from the water, and are so large that they form a heterogeneous mixture of particles that can be seen with the naked eye. Some particles are just the right size to make a colloid with water. Depending on the particle size of the cornstarch you used in your experiment, you either made a colloid or a suspension. You can easily find out by letting your cornstarch-water mixture sit for some time. If the cornstarch separates from the water, the cornstarch particles are large enough to settle down, which means you made a cornstarch-water suspension. If you do not see any separation at all, you have made yourself a colloid!

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