if a balloon is high up it will pop because pressure here think of it like this when you swim and go under water lets say 12ft you will notice that your head will hurt and it will take your oxygen away faster just like a balloon it has air in it so when it goes to high it will pop because its made of weak material so it will pop. and a low balloon because it will hit things and like i said balloons pop easy it could also get soft rubber because it is not moving and if like the sun was on it than it would pop as well i really hope this helped you
