Which frequency makes the best cornstarch monsters?
Written by Jack Spangler
I saw a video on the Internet where someone put a mixture of cornstarch and water into a speaker and the thick liquid looked like it came alive… like a monster. However, the video didn’t explain how it worked. I need to find out if any sound will vibrate the liquid or if there is a specific sound that makes the best cornstarch monster. Here’s my hypothesis… I think that a high frequency will make the liquid vibrate or move the most.
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!
How Does It Work?
After I completed my tests with my Dad, I still didn’t really understand why the lower frequency made the cornstarch move more than the high frequency. To answer the question, I interviewed a professional sound engineer, Mr. Howard Megregor from Engineering Dynamics.
When I visited his laboratory, he set up his own version of my experiment using his very expensive speaker, amplifier and tone generator. When I told him that 20 Hertz worked the best, he dialed in the same frequency and he said that I was correct. Mr. Megregor told me that a “Hertz” is a measure of how many cycles (like a vibration) there are in a second. The high frequency has lots of vibrations, but there is not enough motion in the speaker to vibrate the cornstarch liquid.
Science Fair Connection
Cornstarch Monsters is a great example of a science fair project because it clearly shows the scientific method in action. Jack Spangler chose the frequency of the sound as the only variable to test. He didn’t change the frequency and the type of speaker or the type of sound or the volume. He controlled the variables and even used the same cornstarch mixture for each test so that the tests were fair. He ran a new test each time he changed the frequency and then compared the results. He wasn’t ashamed to say that his hypothesis was incorrect. The best part of the experiment is that Jack still had more questions and followed up on them with an expert. That is some real world learning!
Cornstarch Monsters is definitely a “Science Fair Certified” project. Even if Jack’s subject isn’t of interest to you, this experiment is a great one to look at to show you the thought process and steps involved in a great science fair project.
This is the first science project where I had to perform this many tests to finally arrive at an answer. My first hypothesis was wrong and this made me create a new test. When that test didn’t work, I made up another test. The data from each test (how much it vibrated) helped me decide what test to run next. I had to be reminded several times not to change anything other than the frequency. Now I’m going to put my discovery on YouTube and explain how I did it so that someone else can recreate my experiment.