Cornstarch Monsters – Science Fair Experiment

An awesome visualization of sound waves and frequency using oobleck!

If you’ve ever watched an action movie in a theater, you’ve seen and felt an onscreen explosion. Did you know that what you were feeling was actually waves of sound from the theater’s speaker system? We’ll show you how you can visualize the sound vibrations and explain why, even though you can’t always see it, you can feel sound.

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Experiment Materials

  • Speaker
  • Garbage bag or plastic wrap
  • One box of cornstarch
  • Large mixing bowl
  • Pitcher of water
  • Spoon
  • Gallon size zipper-lock bag
  • Newspaper or a plastic drip cloth to cover the floor
  • Water

Experiment Videos

Experiment

1

Mixing Up a Non-Newtonian Fluid

For this demonstration, you’re going to need to mix up a bit of non-Newtonian fluid, or oobleck. This oozy, gooey glop behaves like a solid and a liquid at the same time and is perfect for our activity.

Pour approximately 1/4 cup of cornstarch into the mixing bowl and slowly add about 1/2 cup of water. Stir. Sometimes it is easier to mix the cornstarch and water with your bare hands.

2

Continue adding cornstarch and water in small amounts until you get a mixture that has the consistency of honey. It may take a little work to get the consistency just right.  The mixture gets thicker or more viscous as you add more cornstarch.

3

Notice how the substance is neither 100% solid nor 100% liquid – you can roll it into a ball, but the moment you stop rolling it turns back into a dripping liquid.


4

Sound You Can See

Gently lay your speaker on its back so that the speaker faces upwards. Make sure that your sound system is off.

5

Cover the speaker with thin plastic like a trashbag or plastic wrap.

6

Pour the non-Newtonian liquid onto the plastic on top of the speaker cone.

7

Turn on your sound system and turn up the volume. Pick a track that has a low, consistent bassline and press play. (You can also download the audio track that we use.) Watch the non-Newtonian fluid come to life!

How Does It Work

You probably noticed that lower frequencies (the sounds of an explosion or bass in a song) subjected the oobleck to much more movement. Knowledge about sound waves, however, might lead you to believe that it should be the exact opposite. The higher pitched sounds have a higher frequency (meaning there are more vibrations per second). But more vibrations don’t equal more movement of the non-Newtonian fluid.  Instead, it is the lower pitched (lower frequency) sounds that cause the oobleck to shake.  Although there are fewer vibrations per second at lower pitches, these frequencies cause more motion in the speaker cones.

Take It Further

For more information on oobleck, the non-Newtonian fluid, check out this experiment: Non-Newtonian Cornstarch Recipe.

Science Fair Connection

Creating dancing oobleck is pretty cool, but it isn’t a science fair project.  You can create a science fair project by identifying a variable, or something that changes, in this experiment.  Let’s take a look at some of the variable options that might work:

  • Try different sounds pitches/frequencies.  Do higher or lower pitches make the oobleck move more?
  • Try different volume levels. How does the volume level affect the oobleck’s activity?
  • Try different ratios of cornstarch to water when mixing the oobleck. Can you find the ratio that shows the most movement?

That’s just a couple of ideas, but you aren’t limited to those! Try coming up with different ideas of variables and give them a try. Remember, you can only change one thing at a time.  If you are testing different sound pitches, make sure that the other factors are remaining the same!