An open system can exchange energy and particles with the environment. The energy of the system and the number of particles does not remain constant. The composite system consisting of the system of interest and environment will be called universe. The universe is an isolated system and the results from micro-canonical ensemble are applied to obtain the conditions that the system and the environment may be in equilibrium. These conditions are temperatures, the pressures, and the chemical potentials of the environment and the system be equal.
An open system can exchange energy and particles with the environment. The energy of the system and the number of particles does not remain constant. The composite system consisting of the system of interest and environment will be called universe. The universe is an isolated system and the results from micro-canonical ensemble are applied to obtain the conditions that the system and the environment may be in equilibrium. These conditions are temperatures, the pressures, and the chemical potentials of the environment and the system be equal.