Why does helium balloon goes high up in the sky ater immediately releasing it? whereas if any other gas is filled inside the balloon, it does not do so

1 Answer
Nov 19, 2016

Answer:

For the same reason that a boat floats on water, or oil floats on vinegar. There is a net buoyant force upwards.

Explanation:

You could have filled the balloon with dihydrogen gas, which would have half the mass of a helium-filled balloon of equivalent size. If the volume of air displaced by the balloon has more mass than the mass of gas inside the balloon, PLUS the mass of the balloon itself, then the balloon will float inasmuch there is a net buoyant force.

This goes back to old Archimedes' principle:

#"Any object, wholly or partially immersed in a fluid,"#
#"is buoyed up by a force equal to the weight of the fluid"# #"displaced by the object."#

So here's a chemistry question to go with the physics. Why should a helium filled balloon or dirigible be preferred to a hydrogen-filled balloon given that the mass of the hydrogen is HALF that of the helium? Note also that since the dihydrogen molecule is LARGER than the helium atom, we would need a less specialized membrane with which to construct the balloon.