We say the cause of perfume disappearing is evaporation. Evaporation gets blamed for a lot of things people forget to put the top on. To most people solutions mean finding the answers. But to chemists solutions are things that are still all mixed up. In looking at a drop of water under a microscope, we find there are twice as many H's as O's.
Clouds are high flying fogs.
I am not sure how clouds get formed. But the clouds know how to do it, and that is the important thing. Clouds just keep circling the earth around and around. There is not much else to do. Water vapour gets together in a cloud.