It is unclear whether the work is defined considering opposite force on the same body or in ideal case where there is a single force acting on a body.If we consider ideal case where only a single force is present on the body, the displacement will not attain a specefic value. It will go on increasing and we cannot fix the value of displacement, I mean when do we say a force has worked on a body? Do we say this when a certain force has to' work' against another opposite force to cause displacement? I think the work is defined considering 2nd case since only then we can have a fix value of displacement because when one force is removed the other force will eventually stop the body.
Think of temperature as average kinetic energy of the water molecules. While the average molecule doesn't have enough energy to break the inter-molecular bonds, a non-average molecule does.

Water is a liquid because the dipole attraction between polar water molecules makes them stick together. At standard atmospheric pressure (acting somewhat like a vice), you need a comparatively large temperature of 100°C (translating to a high average energy distributed among the micsroscopic degrees of freedom, most relevantly the kinetic ones) for water molecules to break free in bulk, creating bubbles of water vapour within the liquid.

However, at the surface of the liquid, lone molecules may end up getting enough kinetic energy to break free due to the random nature of molecular motion at basically any temperature. On the flip side, water molecules in the atmosphere may enter the liquid at the surface as well, which is measured by equilibrium vapour pressure.
