This experiment uses a mixture of cornstarch and water to discover what effect sound frequency has on the shape of the mixture. Students begin by forming a hypothesis about whether a higher or lower frequency will make the mixture move more, and then they observe the results, using the scientific method.
This activity was done with an afterschool group in the public schools with elementary school students with visual impairments.
Test #1 – High Frequency 1000 Hz – I lined the speaker with a plastic bag and poured the cornstarch into the cone. I set the tone generator to 1,000 hertz (1 hertz = 1 cycle per second). I kept the volume constant at “5” in each one of my tests. As you can see, the cornstarch did not vibrate at all. The tone sounded very high pitched. I discovered that my hypothesis was wrong, so I needed to conduct some more experiments.
Test #2 – Try 500 Hertz – Changing the frequency will be my variable. I tried 500 Hertz and the results were disappointing. Nothing really happened.
Test #3 – Try 100 Hertz – This was a good test because I saw the cornstarch mixture start to vibrate for the first time. It looks like the low frequency makes the cornstarch and water move the most.
Test #4 – Try 50 Hertz – I set the tone generator to 50 Hertz and turned the volume up to “5” and the cornstarch monsters started to appear (just like I had seen online). I learned that 50 Hertz means that the speaker vibrates back and forth 50 times a second. You can see in the picture how the cornstarch mixture started to move. Lower?
Test #5 – Try 20 Hertz – The experiment using 50 Hertz shook the speaker so much that it tore the plastic and actually started to tear the speaker. My Dad repaired the speaker and I got a new bag. I used the same cornstarch from the last experiment to make sure I kept everything the same. As you can see, 20 Hertz is the best frequency!
Original experiment from https://www.stevespanglerscience.com/
By Patrick Ryan
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