Sari on Science: Creepy screaming balloons for Halloween

This time of year, there’s nothing like creating a spooky atmosphere. My daughter loves to try to scare people, so we spent some time exploring sound by making screaming balloons to add to her arsenal of scare tactics in time for Halloween. You can try this experiment at home, too, with just a few simple items from around the (haunted?) house.

Did you know that some humans like to be scared? When we feel fear, our bodies get a rush of adrenaline and release endorphins and dopamine, which are actually feel-good chemicals. Once the fear subsides, we can be left with a pleasant and sometimes addicting sense of well-being.

Supplies

• One balloon — 9 inches or larger
• One hex nut (a quarter inch works well, but any size will do)
• Extra balloons (optional)
• Pennies, marbles, seeds or other small objects (optional)

Directions

1. Place a hex nut inside of the balloon; make sure it falls to the bottom.
2. Have an adult blow up the balloon so it’s about half or three-quarters full of air.
3. Tie off the neck of the balloon so no air can escape.
4. Hold the balloon downward, so that the tie is at the top, in the palm of your hand, and your fingers are keeping it in place.
5. Swirl the balloon in a circular motion; the nut may bounce around the balloon in the beginning, but it will eventually roll around the inside of the balloon.
6. As the hex nut rolls inside, listen to your balloon scream! What happens when you swirl the balloon faster versus slower?

What’s happening?

This experiment actually demonstrates two different things: sound and motion. Balloons are smooth, and as the hex nut rolls around, its six sides allow for the flat edges to vibrate along the inside of the balloon. This vibration is what creates the screaming sound that you hear. As you swirl the balloon, centripetal force is acting on the hex nut, and that is what keeps it moving in a circular motion around the inside of the balloon even when you stop swirling it. Eventually, friction and gravity slow it down.

Note: the balloon will pop if you swirl it a lot, because the hex nut will wear down the polymers that make up the balloon.

Try this experiment again with a different sized hex nut. Does it make a different sound? Try to inflate different sized balloons. Does this make a difference in sound? Try to use a different object inside the balloon. Does the balloon still “scream?” How quiet can you make your balloon scream while still producing a sound? Find more great science activities online at azscience.org

RELATED: More “Sari on Science” projects

Read this month’s Raising Arizona Kids Magazine!