What happens to the speed of molecules in water vapor when it condenses to form a liquid? . a) the molecules slow down.. b) the molecules speed up. c) the molecules slow down and then speed up. d) the molecules speed up and then slow down.

The correct option is A. Water vapor is in a gaseous state and the molecules of the gases have great kinetic energy to move about randomly. When the water vapor condenses to liquid, the intermolecular forces among the molecules of water is closer together than in gases, this will make the particles to lose some of their kinetic energy and their motion will be slowed down.