Equilibrium
Equililibrium is recongnized as a static condstion in which, with time, there is no change at all in the macroscopic properties of of a system, and this envolves all potentials that can make a change. In engineering, the equilibrium is justified when a process gets exact results. For example, in a re-boiler of a distillation column is considered an equilibrium between vapour (v) and liquid (l) phases.
An isolated system that has l-v phases in contact, reaches with time a final state in which there is no tendency to have any kind of change. Temperature, pressure and phase composition reach final values that keep fixed. But at a microscopic level there is still motion. The molecules contained in a phase at a determinate time are different that the ones that are in the same phase at a different time. Molecules that are close to the boundary of both phases, usually have enough velocity and strength to go through one phase to another.
An isolated system that has l-v phases in contact, reaches with time a final state in which there is no tendency to have any kind of change. Temperature, pressure and phase composition reach final values that keep fixed. But at a microscopic level there is still motion. The molecules contained in a phase at a determinate time are different that the ones that are in the same phase at a different time. Molecules that are close to the boundary of both phases, usually have enough velocity and strength to go through one phase to another.
References.
Smith, J. (2007). Introducción a la termodinámica en Ingeniería Química. México: McGraw Hill.
Smith, J. (2007). Introducción a la termodinámica en Ingeniería Química. México: McGraw Hill.