Question

Why does a plastic bottle that is sealed at a high altitude change its shape when it is taken to a low altitude?
The number of gas molecules that strike the outside of the bottle increases as altitude decreases.
The number of gas molecules that strike the outside of the bottle decreases as altitude decreases.
The bonds between the molecules of the plastic bottle become weaker as the altitude decreases.
The bonds between the molecules of the plastic bottle become stronger as the altitude decreases.

Answer 1

The first statement is correct: "The number of gas molecules that strike the outside of the bottle increases as altitude decreases."

Reason: Atmospheric pressure comes from air molecules hitting surfaces. At lower altitude the air is denser so more molecules strike the outside of the sealed bottle, producing a higher external pressure than the internal pressure it was sealed at—so the bottle is pushed in. The changes in plastic bonding are irrelevant.