With five kids in my house, we have a multitude of birthday parties each year. Whether we have a big gathering at home or an intimate dinner out, we try to make birthdays special. Part of what makes each birthday special is the decorations. What’s a birthday celebration without balloons?? Balloons filled with helium!
I never grow tired of seeing the wonder on the face of a child who sees a helium balloon for the first time. And I’ve had more than my share of belly laughs over pets who are absolutely terrified of the colorful, floating orbs. What must they think? Seeing these objects that defy the laws of gravity?
But how do they work? What makes them float? How do they fly?
It comes down to weight. The air we breathe is largely made up of nitrogen. Nitrogen weighs 1.2506 grams per liter. Helium weighs only 0.1785 grams per liter. The lightweight helium displaces the heavier air. The pressure from the air around the balloon (along with the temperature of the air) “pushes” the balloon upwards.
It is very similar to how objects float in water. Have you ever tried to hold a sealed, empty, plastic bottle underwater? That can be a workout! This is because the bottle is buoyant. The air in the bottle is lighter than the water around it. Therefore, the bottle is “pushed” upward. Just like the bottle is buoyant in water, a helium balloon is buoyant in air.
Why does helium make my voice squeaky?
Disclaimer: DO NOT inhale helium. It can be dangerous, or even fatal.
When we speak, vocal chords in our throat vibrate, and that’s what makes the sound of our voice. Think of how the strings vibrate on a violin or guitar to make music, your throat is similar. The density of the air around us, causes our vocal chords to vibrate at a certain speed.
When a person breathes in helium, it travels over their vocal chords. Helium is not as dense as air. Therefore, vocal chords do not have to work as hard to vibrate, so they vibrate faster! The faster the vibration, the squeakier the person’s voice.
Have fun with balloons.
Science is everywhere.
Who knew that we could learn so much about buoyancy and vocal chords from a simple helium balloon? Science is all around is in “everyday” objects. I encourage you take a look around you and find the science in your every day!
Science is everywhere! Learn more in The Homeschool Scientist’s Science Is Everywhere monthly series!