of liquid on the surface of a small droplet are held less tightly compared to atoms on a flat (bulk) liquid surface.High curvatures effectively reduce the coordination number of the
surface atoms making them easier
to evaporate.Thus the liquid has a
higher vapor pressure over small
liquid droplets compared to bulk liquid.The effect of curvature on the
vapor pressure of liquids is the Kelvin effect.
Positive curvature:liquid in drops has a higher vapor pressure that bulk.
Negative curvature:liquid in pores has a lower vapor pressure than bulk.
The vapor pressure P relative to the bulk P0can be found using the Kelvin equation, show here for spherical surfaces of radius r.
The other parameters are: γ the surface tension, the molar volume of the liquid, R the gas constant, and T the absolute temperature.