The temperature changes by it gets colder than hotter than colder then hotter as you go higher because of the air pressure.
The atmosphere protects us from most of the sun uv rays and from metors and many more things that the atmosphere protects us from.
the pressure changes by going up there is less air pressure
the air pressure looks like nothing you can't see it but when you go higher up you can feel it like if your in a airplane your ears will pop because of the air pressure .
nitrogen - 78% oxygen - 21 % other - 1% those are the gasses