Question: If water vapour rises into the atmosphere after evaporating, and turns into a liquid by condensing, why does it go into the form of a cloud and not just drop back to the ground straight away like most liquids would if dropped from a high place?

Oli Wilson answered on 8 Nov 2017:

Interesting question, it had me scratching my head for a bit! I think the key is the size of the water droplets. When water from the sea or a puddle evaporates, it’s a gas – not droplets at all. As they rise into the atmosphere they cool down and start to turn into tiny little droplets – but these are so small the air around them can hold them up. That collection of water droplets is a cloud. If the cloud gets much colder, or more vapour gets jammed into it, the water droplets start to stick together until eventually they’re too large and heavy for the air to keep supporting them. Then, they do exactly as you say, and fall to the ground like any other liquid from up high 🙂