# Is inconsistent when a liquid evaporates, its volume changes, and pressure and temperature are constant?

We know that ordinarily, pressure, volume, and temperature cannot change individually without one affecting the other. Yet when a liquid evaporates, its volume changes, even though its pressure and temperature are constante. Is this inconsistent?

(From University Physics with Modern Physics 13th Edition)

I think it is inconsistent because when, for example, water evaporates two things occur:

1. The temperature remains constant. In phase transition, the water temperature remains unchanged.
2. The pressure CHANGES because there is less volume.

I am not very confident with the second part (2).

What do you think?

• InfZero, you need to be more specific. If water evaporates in an open container, its pressure is equal to the ambient pressure. "Less volume" probably doesn't apply in this case. If water evaporates in a closed container, this will cause the pressure to increase. And note, at constant temperature, there is an equal amount of water evaporating and condensing in a closed container, so the pressure stays constant. – David White Feb 19 '17 at 19:49
• Consider the conditions under which "We know that ordinarily, pressure, volume, and temperature cannot change individually without one affecting the other. " has actually been examined up to this point in your education. Are they consistent with the process that you are considering now? – dmckee Feb 19 '17 at 20:40