Some oxygen molecules help fires burn while others help make water, so sometimes it's brother against brother. 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 and around.
There is not much else to do. Water vapor gets together in a cloud. When it is big enough to be called a drop, it does. H2O is hot water, and CO2 is cold water. To collect fumes of sulphur, hold a deacon over a flame in a test tube.