I think that a gas cloud is best described as a clump of very
very tiny water droplets suspended in the air. But that's
really a guess on my part. A cloud doesn't keep its shape
and/or its size forever. If you watch a cloud as it goes
across the sky you will see its edges fluctuate...and eventually
when enough water droplets condense into a cloud, the tiny
droplets tend to form larger droplets, which can no longer
be held aloft by the winds and fall as rain (or snow if it's cold).