Why do balloons gradually lose it's helium?

Question

Why do balloons gradually lose it's helium?

Answer 1

Helium balloons slowly deflate, because helium atoms can get through the wall of the balloon (and escape) by diffusion.

In this case diffusion is quite fast, because helium atoms are very light (they've got low atomic mass) and the wall of the ballon is very thin.

Answer 2

Balloons gradually lose it's helium(or any other gas) after some given amount of time due to diffusion. The air molecules slips through the small holes or empty spaces on the inflated balloon. The balloon doesn't appear to have holes but they have small enough holes which allow atoms to escape. The amount of time it takes depends on the molecular weight of the gas. A balloon of Helium would lose its gas before a balloon filled with the air you put into it (CO2 carbon dioxide).  

Answer 3

The latex balloons are slightly porous and the helium can leak right out of the walls of the balloon. Air molecules are larger than helium molecules so they leak out more slowly, so an air-filled balloon deflates more slowly as well. Mylar balloons are not nearly as porous and will remain infalted for much longer.

Answer 4

I was told that helium flies because it is actually made of tiny angels.  After a while they die inside the balloon and go back to heaven where they start over, which is why clouds fly so easily, but I don't believe any of it.

The atoms inside the balloon are able to pass between the atoms of the walls of the balloon and therefore escape.  This is easily caused by the pressure from within.  Balloons look impermeable, but they aren't.