condensability

Condensability is the tendency of a substance in the gas phase to change to the liquid phase under suitable conditions of temperature and pressure. In thermodynamics and physical chemistry, it is assessed via vapor–liquid equilibrium and phase diagrams, which delineate the saturation line separating stable vapor from liquid and the sub- and super-saturated regions.

Condensation occurs when the chemical potential of the vapor exceeds that of the liquid, which for a given substance can be predicted by the Clausius–Clapeyron relation that describes how the saturation pressure varies with temperature. Condensability is higher for substances with strong intermolecular forces and relatively high boiling temperatures at ambient pressure; less condensable gases require greater cooling or compression to reach the condensation boundary. The critical temperature and pressure bound the conditions under which a substance can be condensed to a liquid.

In real systems, mixtures may contain non-condensable gases that do not readily condense under operating conditions. These non-condensables affect heat and mass transfer and can raise the practical condensation pressure or reduce condensation rate.

Applications include distillation, refrigeration, and natural gas processing, where the condensable components are separated from inert or non-condensable gases. In atmospheric science, the term describes the potential for water vapor to form liquid droplets, driving cloud formation when humidity approaches saturation.

Examples illustrate that water vapor is highly condensable under typical atmospheric conditions, whereas many inert gases require substantial cooling or pressure changes to condense. Condensability thus links phase behavior to practical design and natural processes.