Question

1. Since gases are matter why do some float away from gravity?


Probably a dumb question

wat.

they dont "float away" they simply sink. like a rock in a pool, the heaviest gases will fall to the bottom of our atmosphere however since gases are typically close in weight, their heat also plays a great role in their distribution on our planet. we observe this as wind.
gases get "blown" away or eroded away from planets due to solar wind

gasses are matter but broken up into small particles... if that particular gas particle is less dense than air at that altitude it will float... if its more dense it will sink. And also through diffusion the gas will slowly spread out until its spread out evenly in its givin space

There are other theories of gravity, some involve particles, common thesis is due to the gravitational attraction of the gas particles, and thus ourseleves - would never have existed to 'float away'!