Question

Whats happens to the energy when you fill up a ballon with air and then release the ballon?

Answer 1

What happens to what energy? There are a lot of interactions here.

Ultimately, the air pressure held under elastic potential energy from the balloon rubber goes to kinetic energy of air molecules and other heat exchanges.

Answer 2

And the kinetic energy of the balloon itself, of course, as it goes flying around the room..

Answer 3

And then the balloon eventually hits walls and then the floor transferring energy in the form of heat and internal energy of collision objects increases slightly..