Vacuums are nothings. We only mention them to let them know we know they're there. The cause of perfume disappearing is evaporation. Evaporation gets blamed for a lot of things people forget to put the top on. I'm not sure how clouds are formed, but clouds know how to do it, and that's the important thing.
Water vapor gets together in a cloud.
When it is big enough to be called a drop, it does. Rain is saved up in cloud banks. It is so hot in some places that people there have to live in other places. Mushrooms always grow in damp places, which is why they look like umbrellas. Momentum is something you give a person when they go away.