Think about putting some whipped cream on top of a cup of hot chocolate. The whipped cream floats on top because it’s lighter than the hot chocolate. Helium does the same thing in air. It wants to float to the top. Of course, if we have a string tied to our balloon and keep a firm grip on it, the balloon will stay anchored near the ground.
The tiny pieces that make up helium are smaller and lighter than any other gas with the exception of one: hydrogen. People like to use helium instead of hydrogen for one important reason. Hydrogen burns and helium does not. It’s much safer to use helium!
ExplorationSinking Party Balloons
Have you ever had a birthday party in your home with lots of balloons? A couple days later, the balloons just don’t look as good as they did at your party. They shrink up and get wrinkly. What’s happening to the gas inside them?
It’s leaking out into the air through tiny holes in the balloon! The holes are so small that most things – like water – can’t get through them, but helium and regular air are even smaller than water. Eventually the gases find their way through the holes and escape, leaving the balloon smaller. If super light helium gas escapes a balloon, the balloon gets heavier, and starts to sink.
So which deflates (loses its air) faster? A balloon filled with helium or a balloon filled with regular air?
This might be very interesting to watch if you ever have a party with both types of balloons. The helium balloons will lose their gas much faster, because the tiny bits of helium are much smaller than the tiny bits of air. A balloon filled with regular air can last many days longer than a balloon filled with helium. Air has a harder time escaping!
Because gas slowly but surely escapes from balloons, you never want to blow up balloons too far ahead of a party. They might not look very impressive by the time your guests arrive!