Any change in the physical world is consequent to a net force levelling down available energy. Different features of a system, or process, can determine on which properties of the system the levelling force eventually operates. Examples are the equilibration of the pressure of a gas, of the temperature of bodies, of the concentration of solutions, of the position of a body with respect to a fluid in the presence of a gravitational field, and so on. All these phenomena occur because of the levelling force and are associated with an entropy increase. The entropy increase can be calculated through specific relationships.
Keywords: Accessible microstates, Chemical potential, Colligative properties, Conjugate pairs, Equal multiplicity, Extensive variables, Fundamental equation, Intensive state functions, Lost work, Multiset permutations, Overall entropy increase, Particles concentration, Reversible change, Saturation, Spontaneous transfer, Standard conditions.