Why is hydrogen used to inflate hot air balloons?
Hydrogen is not used to inflate hot air balloons. Just regular air is used which is then heated to make the balloon more buoyant as hot air weighs less than cold air. Hence the name hot air balloons.
'Hot air' balloons don't use hydrogen. They use hot air. Balloons that use hydrogen are not referred to as 'hot air' balloons. The only balloons that can accurately be referred to as 'hot air' balloons are the members of the balloon population that derive their lift/buoyancy from the presence of hot air. Of course, if a balloon used no hot air, then it could freely be referred to as a 'hydrogen' balloon, a 'helium' balloon…
Hydrogen, until the Hindenburg,then everyone realized that "Hey, Hydrogen isn't that safe to use!" Hot air balloons, you mean?? Just air that is hot. Actual hand balloons and such? Helium or again, just air. Helium floats better because it is lighter than the surrounding air around it. Helium and air are still used in both.