Kelvin equation

The Kelvin equation relates a liquid’s equilibrium vapor pressure to the curvature of its surface. It predicts higher vapor pressure over convex droplets and lower vapor pressure over concave menisci than over a flat surface.

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Young–Laplace equation: A relation connecting pressure differences across a curved interface to surface tension and curvature. It supplies the pressure jump that drives the Kelvin equation’s vapor-pressure shift.
Kelvin effect: The increase or decrease in equilibrium vapor pressure caused by a curved liquid surface. This names the vapor-pressure phenomenon quantified by the equation.
Vapor pressure: The pressure exerted by a vapor in equilibrium with its condensed phase at a given temperature. The equation predicts how this equilibrium quantity departs from its flat-surface value.
Ostwald–Freundlich equation: A relation describing how a small crystal’s solubility depends on its curvature. It is a closely related curvature correction for solid–liquid solubility rather than liquid–vapor pressure.
Chemical potential: A thermodynamic quantity measuring how a system’s free energy changes when matter is added. The equation follows by balancing chemical potential across curved liquid and vapor phases.
Capillary condensation: The condensation of vapor in small pores at pressures below saturation over a flat surface. Concave menisci lower equilibrium vapor pressure, allowing pore filling at reduced humidity.
Laplace pressure: The pressure difference across a curved interface caused by surface tension. It links interface curvature to the liquid pressure used in the thermodynamic derivation.
Clausius–Clapeyron relation: A thermodynamic relation connecting phase-transition pressure and temperature along a coexistence curve. It describes temperature dependence of phase equilibrium, not the curvature correction at fixed temperature.
Gibbs–Thomson effect: The dependence of a phase’s equilibrium properties on the curvature of its interface. It expresses the same curvature-driven shift in phase equilibrium beyond vapor pressure.
Köhler theory: A theory describing how curvature and dissolved solutes determine water-vapor equilibrium around cloud droplets. It combines the Kelvin curvature effect with solute-driven vapor-pressure lowering.