We hear sound all the time, but have you ever wondered what it looks like? In this experiment, we’ll create sounds we can both hear and see using the properties of waves! We’ll also learn how sound travels through different materials and about the energy it carries.
Materials
Bowl
Plastic wrap
Salt or pepper
Pot (optional)
Large spoon (optional)
Time Estimated:
10 minutes
Directions:
First, cover the top of the bowl with plastic wrap. Make sure it’s tight; the top shouldn’t have any wrinkles!
Next, sprinkle on a thin layer of either salt or pepper. Use whichever one you can see better.
Now, place your mouth on the side of the bowl and hum. Watch what happens!
You can also try banging the pot and spoon together while standing beside the bowl. How does the movement change?
Think Like a Scientist!
Why does the salt/pepper move?
Why does it move differently when we bang on the pot?
How Does it Work?
Did you know that sound is really just vibrations traveling through a medium (or a material)? These vibrations are called waves, and normally they travel through fluids like air or water. However, sound can also pass through solid objects— like our plastic wrap! When we hum on the bowl, the sound waves make the plastic vibrate and the salt moves along with it. You may have noticed that the salt closest to our mouth moved the fastest when humming on the bowl. This is because sound is made of energy. The sound waves made the plastic molecules (the tiny things the plastic wrap is made of) bump into each other and lose energy as heat. Because the wave had to pass through more plastic to get to the other side, it lost more energy and vibrated less when it got there. However, when we banged on the pot, we created a much louder sound. Louder sounds carry more energy, so the waves could pass through without being noticeably slowed down. This is why all of the salt moves the same when banging the pot!
Further Exploration:
The study of sound is called acoustics, and all types of scientists study these special waves. Botanists study plants and how they interact with their environment, and recently, they’ve been exploring how plants respond to sound. As we’ve seen, these waves cause the material around them to vibrate. Instead of hearing these vibrations like we do, plants feel them as mechanical (physical) stimuli. In fact, it’s been shown that some sounds help plants grow more fully and quickly!
Looking for more fun at-home STEM activities for your young scientist? Check out our workbook full of exciting science experiments and empowering activities!
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