vapour-liquid equilibrium

Vapor-liquid equilibrium (VLE) occurs when a liquid and its vapor (gas phase) coexist in a stable state, with the rate of molecules evaporating equal to the rate of vapor condensing back into liquid. At specific conditions of temperature and pressure, these two phases balance each other perfectly. This means the amount of liquid and vapor remains constant over time, even though molecules continuously transition between phases. VLE is important in processes like distillation, where separation of components depends on understanding and manipulating this equilibrium.