Sound is a movement which is handed on from atom to atom in a gas through which the sound is passing, just as a chain of workers pass buckets of water to a fire. The quicker the workers move their hands and arms, the quicker the water moves.
In a gas, motion has the upper hand; the atoms are moving so fast that they have no time to enter into any sort of combination with each other: occasionally, atom must meet atom and, so to speak, each hold out vain hands to the other, but the pace is too great and, in a moment, they are far away from each other again.
When a liquid boils, the temperature has been raised to such a pitch that the evaporating molecules are sufficient in number and speed to lift off the air from the surface of the liquid and push it back en masse.
