Re: how does condensation form?

Condensation forms when water molecules in relatively warm air come
into contact with a cold surface.  As the molecules cool down, they
begin to move about more slowly and draw closer together.  If they
are cooled down enough, they begin to stick together -- they no longer
have the energy to overcome their natural attraction for one another.

(It sounds like a soap opera plot, doesn't it?)

As more and more molecules stick together, visible droplets of liquid
water form on the surface.

This, incidentally, is the same process that creates rain.  The "cold
surface" is a mass of cooler air in the atmosphere.  Water starts to 
condense on the surface of tiny dust particles in the air, and form 
raindrops.