Last month we heard a popping sound when the pressure inside a straw was increased and then suddenly popped. Let’s look at how we were able to hear that sound.
Materials:
- Bowl
- Saran or plastic wrap
- Sugar or salt or rice
- Something to make noise with
Experiment:
Cover the top of a bowl tightly with the plastic wrap. You may need adult help for this. Sprinkle the salt, sugar, or rice onto the plastic wrap. Get close to the edge of the bowl and hum loudly or bang on something next to the bowl. You may even put your top lip on the edge of the bowl while you hum.
What’s happening?
You should see that the solid particles are bouncing around on the plastic wrap. Sound is all about vibrations. When you hum, you are causing vibrations. Your humming causes the air molecules to vibrate or move back and forth. When they do this, they hit molecules next to them which then do the same thing. They keep passing this energy along. When those vibrations hit the plastic wrap, they cause the plastic wrap to vibrate which causes the solid particles to vibrate or bounce. The same thing happens when you bang on a drum, and the tight skin over the drum vibrates causing the drum to make the noise.
Extension:
Are there other items that make sound that are effective at causing the solid particles to jump around such as a kazoo or other musical instrument? You can also get extreme with it by putting oobleck on a speaker as seen here:
https://www.youtube.com/watch?v=HojmEUFall8.
For a real wild ride in viewing sound waves go see the Blue Man Group!
References:
https://premeditatedleftovers.com/naturally-frugal-mom/sound-and-volume-vibrations-science-experiment/
https://www.youtube.com/watch?v=W2h3VVVlpls
To view past “ChemShorts for Kids” activities, go to:
https://chicagoacs.org/ChemShorts.
