Question

A fog over a lake. what two changes of state must occur to produce the fog? do the water molecules absorb or release energy during these changes of state? what happens to the motion of the water molecules as a result?

Answer 1

Evaporation and condensation occur due to daytime heating of the water molecules in the lake. They absorb heat and transform, water molecules rise into the air forming the fog cloud. 

Answer 2

The water from the lake must first evaporate from the liquid state to the gaseous state and then condense in the air to form vapors.
The water molecules absorb energy while evaporating and release it when condensing. Their motion gets faster when they are evaporating and slows back down upon condensation.