My son heard that a helium baloon, if let go, can go up so high until the pressure causes it to bust.
He wants to know:
How high before bursting?
It depends on the strength of the balloon and how much helium was put in.
If the balloon was filled almost to the breaking point on the ground, it wouldn’t rise very far before it burst.
But if just enough helium was put in to get the balloon to start rising, with plenty of room to expand, it could rise very far indeed.
I imagine that a balloon could be made such that its weight would equal the helium’s buoyant force at some altitude before it burst, at which time it would stop rising and just float around until it was sucked into a jet engine.
There’s too many variables to make it stable enough to do this. Heat, for one thing. Variations in local air pressure for another. That’s why balloonists failed for decades in their attempts to circumnaviagte the globe.
Using a material like latex, which stretches more or less elastically right up to its ultimate strength, this isn’t possible. It’ll actually rise at a very nearly constant rate after being released, given expansion of the balloon and the density and pressure profiles of the atmosphere.
When I was in elementary school we released helium balloons to see which would go farthest. Each balloon had a card on it that the finder was supposed to mail back. My card was never returned, but one girl’s balloon was found in Canada, several hundred miles away. Evidently that one didn’t explode, at least not right away.
We did that in kindergarten. I believe one of our balloons made it to Indiana. It even still had some air left in it when we recieved it.
Helium is strange stuff. It does not form molecules, and consequently Helium gas is componsed of individual atoms. Atoms are tiny and will find their way through almost any material. Helium under the slightest pressure will find its way through the skin of a regular balloon in a few days - a metalised balloon will last a little longer. So, I would expect that few Helium filled balloons burst, but that most simply deflate.
Hydrogen, on the other hand, forms molecules of H2. Each molecule weighs half as much as an atom of Helium, but is huge by comparison. If you want to win a balloon race: partially fill a strong balloon with Hydrogen.
It isn’t the size of the molecules that makes a difference, it’s the mass. At a given temperature, molecules of any substance will have the same average kinetic energy, which means that lighter molecules will be moving faster. It’s the faster molecules that have the easier time escaping, so hydrogen will escape even easier than helium.
By the way, helium does have molecules; it’s just that each molecule is only a single atom.