Question

Why doesn't a jar completely full of water evaporate?

A. Water only evaporates when it boils
B. There is no air for it to evaporate into.
C. Water cannot evaporate in a container.
D. Evaporation requires an exchange of gases.

Answer 1

Eventually, the water will all evaporate in this way. The energy which is lost as the particles evaporate is replaced from the surroundings. As the molecules in the water jostle with each other, new molecules will gain enough energy to escape from the surface.

Answer 2

Answer: b: "There is no air for it to evaporate into."

Explanation: If the jar is closed, and filled with water (and it is not heated or nothing like that) the system doesn't suffer any change in his extensive properties nor intensive properties. Now, suppose that there is some energy applied to the water, and it wants to evaporate, this would imply a change in the volume (the volume of the vapor is bigger than the volume of the liquid water) then you will need some free space to evaporate a fraction of water, but there is no free space (the jar is completely filled with water and closed) so there is no space to evaporation. If you give enough energy to the jar, it eventually will break to release this energy.

Then the right answer is b: "There is no air for it to evaporate into."