why when at high altitudes does water bottles, chip bags, etc. expand to maximum capacity?



I recently visited some national parks in California and in sequoia national park, the water bottles, chip bags, sauce packets were all expanded to the point it looked like they could explode at any moment. Why is this?

In: Physics

The air pressure outside drops the higher up you go which causes the bag to inflate with the about of air pressure inside. Sometimes if there isn’t enough room to expand, the explode.

When you change altitude, the density of the air outside the package changes, but the density if the air (or in the case of the chips, nitrogen) does not change because it is sealed. The difference in the pressure will cause the package to expand or contract, depending on whether the outside pressure has increased or decreased.

For example: last week I was in the mountains and had some water, then put the cap back on. Later in the day I went home, near sea level. The atmospheric pressure in the mountains was less than it is at sea level, so the bottle had contracted and shrunk, looking it it had been squished. When I opened the cap, there was a hiss as the pressure inside and outside the bottle became equal and the bottle popped back into its normal shape.