Why Do Balloons Float? [VIDEO] | Science Explanations for Kids (2024)

Ask Tappity: Science Questions for Kids > Why Do Balloons Float?

What keeps birthday balloons up in the air? Watch this video to find out, or read our explanation below!

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Why Do Balloons Float? [VIDEO] | Science Explanations for Kids (2)

Helium is Less Dense than Air

Balloons that float are typically filled with helium gas, which is less dense than the gas in our air. That means a balloon-sized ball of helium weighs less than a balloon-sized ball of air. The difference in density is the key to a balloon`s floatation.

Floating in Air is Just Like Floating in Water

If you put an empty water bottle at the bottom of a swimming pool, it will float to the top - just like a balloon floats in air. And in fact, the same scientific principle is responsible for floating both objects.

Why Do Balloons Float? [VIDEO] | Science Explanations for Kids (3)

Why Do Balloons Float? [VIDEO] | Science Explanations for Kids (4)

The Principle of Buoyancy

If you put your hand in a bowl of water, what happens to the water level? It goes up - submerging your hand requires LIFTING the water your hand pushes out of the way. The same thing is true for anything submerged in liquid, and for anything submerged in air. It takes force to push stuff out of the way, and when it comes to floating, that force is just the weight of the object. So because a balloon weighs less than the air around it, it isn't pulled down hard enough to push the air out of the way. That means the balloon is pushed upwards instead! One way that can be helpful to think about it is to imagine the air sinking underneath the balloon, sort of like honey sinking underneath water.

Balloon Facts for Kids

Got balloon questions? We’ve got balloon answers!

Want to pop a balloon without a bang? Just put a piece of tape on the balloon, and poke a hole through the tape. The tape will keep the balloon from popping, and the air will leak out slowly instead of being released all at once, which is what causes the popping sound.
Balloons pop at around 570 meters per second - faster than the speed of sound!
As a helium balloon gets higher and higher, the air around it is more and more spread out, so it pushes on the outside of the balloon less. That means the helium inside the balloon can push it out even farther, so the balloon actually gets a little bit bigger, until eventually, the rubber stretches too far and pops.
Sometimes, if the rubber on the balloon is strong enough, it will FREEZE before it pops. That's because the higher you go, the colder it gets. Around the height of airplanes, it's even cold enough to freeze rubber. These frozen balloons will pop too, but because they are frozen solid, they'll shatter into a bunch of tiny pieces, like a piece of glass.
Balloons have actually been around for a long time, except they weren’t made of rubber - they were made of animal bladders, which were then filled with air. Balloons were first floated using hot air in the 18th century, and the first modern rubber balloon was made by Michael Faraday in 1824 to conduct experiments using hydrogen.
Humans flew for the first time by using a hot air balloon in Paris on November 21, 1783.
Inhaling helium makes your voice squeaky because the sound from your vocal chords travels 3 times faster through helium than it does through air. The faster soundwaves result in a higher pitch. Another gas, Sulfur Hexafluoride, is heavier than air, and has the opposite effect - it makes your voice sound very deep.
Balloons have been used outside of Earth! In 1985, two weather balloons were placed in the atmosphere of Venus and took measurements such as temperature, pressure, and windspeed.
A procedure called angioplasty uses balloons to open blocked arteries or veins.

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