condensation
/ kon-den-SAY-shun /
Pour a cold drink on a warm day and watch beads of water appear on the outside of the glass, seemingly from nowhere. They came from invisible water vapour in the air, gathering and settling onto the cold surface. This gathering of scattered particles into a denser, more ordered form is condensation.
Condensation is the process by which a spread-out, fast-moving collection of particles draws together into a closer-packed phase. In the most familiar case, a gas becomes a liquid: when vapour is cooled, its molecules lose energy, slow down, and the attractive forces between them finally win, pulling them into the tight ranks of a liquid. The hidden energy the molecules had to give up to settle down is released as heat to the surroundings.
This matters because condensation drives rain, clouds, and dew, and is the cooling step inside every air conditioner and distillery. In modern physics the word reaches further: it also names quantum condensation, where particles pile into a single shared state, as in a Bose-Einstein condensate. A common misconception is that condensation only means water droplets — at heart it is the broader idea of particles condensing together, whatever their kind.
Morning dew on grass is condensation in plain sight: overnight the cold blades chill the surrounding air below the point where it can hold its moisture, so vapour gathers back into tiny liquid droplets that bead on every leaf.
Dew forms as vapour condenses into liquid on cool grass.
Condensation is the reverse of evaporation: one releases heat as particles gather, the other absorbs heat as they break free, which is why sweating cools you but a steamy bathroom mirror grows warm and wet.