jbedow

I know we all learn that when we heat a certain volume of air, as in a balloon, the heated volume will be less dense than the surrounding volume of air, so it rises or floats. But I would like to see a layman's explanation of what is really happening at the molecular level. The energized molecules inside the balloon do not move in unison, they are just moving faster. So why do they "float" above the slower, outside molecules? Am I correct that it is a matter of probability, i.e., that an energized molecule would tend to have more interactions (be stopped) moving down towards denser area of slower molecules than it would moving up towards less dense area of molecules, so in the course of multiple random movements, the energized molecules will have more successes moving up away from denser areas? I appreciate any effort you may spend in explaining this. Thanks