What happens to chip bags when they are high in the atmosphere?

It will explode.

Explanation:

The amount of air in a bag of chips is fixed. If the package was sealed at a lower elevation and carried to a higher elevation the air inside of the bag will swell against the reduced atmospheric pressure. If the bag is not well made it could even burst at the seams.

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me