Question

Why does a plastic bottle that is sealed at a high altitude change its shape when it is taken to a low altitude?

Answer 1

The number of gas molecules that strike the outside of the bottle increases as altitude decreases. 

Answer 2

Explanation: This happens due to the change in the atmospheric pressure around the plastic bottle.

When air is filled in the bottle at higher altitude, the concentration of air molecules is low.

When the same bottle is brought at low altitudes where the concentration of gas molecules outside the bottle is higher than inside the bottle, so the pressure exerted by the higher number of molecules present outside will push the lower number of the gas molecules. Hence, resulting the bottle to shrink.