- Date: 1594
- 1 : the act or process of condensing: as a : a chemical reaction involving union between molecules often with elimination of a simple molecule (as water) to form a new more complex compound of often greater molecular weight
- b : the conversion of a substance (as water) from the vapor state to a denser liquid or solid state usually initiated by a reduction in temperature of the vapor
- c : compression of a written or spoken work into more concise form
Condensation is the change in the phase of matter from the gaseous phase (of an element/ chemical species) into liquid droplets or solid grains of the same element/ chemical species. Upon the slowing-down of the atoms/ molecules of the species, the overall attraction forces between these prevail and bring them together at distances comparable to their sizes.
Since the condensing atoms/ molecules suffer from reduced degrees of freedom and ranges of motion, their prior kinetic energy must be lost/ transferred to an adsorbing colder entity — either a center of condensation within the gas volume (colder molecules of the species, cold grains of dust etc.) or some contact surface. Condensation is initiated by the formation of atomic/ molecular clusters of that species within its gaseous volume — like rain drop or snow-flake formation within clouds — or at the contact between such gaseous phase and a (solvent) liquid or solid surface.
- absorption into the surface of a liquid (either of the same species or one of its solvents) — is reversible as evaporation..
- adsorption (as dew droplets) onto solid surface at pressures and temperatures higher than the specie's triple point — also reversible as evaporation.
- adsorption onto solid surface (as supplemental layers of solid) at pressures and temperatures lower than the specie's triple point — is reversible as sublimation.
Condensation commonly occurs when a vapor is cooled and/or compressed to its saturation limit when the molecular density in the gas phase reaches its maximal threshold. Vapor cooling and compressing equipment that collects condensed liquids is called "condenser".
Psychrometry measures the rates of condensation from and evaporation into the air moisture at various atmospheric pressures and temperatures. Water is the product of its vapor condensation — condensation is the process of such phase conversion.