What will cause a balloon blown up at a low altitude to pop if it is taken to a higher altitude?

If the pressure inside the balloon is too high relative to the pressure outside, the balloon will burst. If you don't overinflate it, the pressures inside and outside the balloon should be equal, so there is no net pressure on the balloon. At high altitudes, though, the atmospheric pressure decreases, but the pressure inside the balloon remains the same - now there is a net pressure outwards on the balloon, which, if sufficiently high, will burst it.

Hey there,
The answer is - The surrounding pressure on the balloon decreases with increase in altitude.

Hope this helps :))

~Top☺

100 pounds is 100 pounds no matter the object or item being weighed