Why do balloons float away?
Floaty balloons are filled with a gas called helium that's lighter than air.
Pip’s answer
- Floaty balloons are filled with a gas called helium that's lighter than air.
- The heavier air all around squeezes in underneath and pushes the balloon up.
- If nobody holds the string, up, up, up it goes!
- Hehe, a balloon filled with your own breath wouldn't float away!
Try it together
Can you float your arms up slowly, like a balloon?
For grown-ups
Helium is much less dense than air. A helium balloon weighs less than the air it pushes aside, so the surrounding air pushes it upward (buoyancy). Your breath is mostly air with extra carbon dioxide, so a balloon you blow up is slightly heavier than air and sinks.
Ask your child: Why does a balloon you blow up fall to the floor?
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