Statistical thermodynamics - General presentation

The aim of statistical thermodynamics is to explain or predict macroscopic phenomena, and to calculate the thermodynamic quantities of a macroscopic system from the microscopic or molecular aspect, i.e. from experimental and theoretical data on the individual particles that make up the system under consideration. The complexity of the problem (immense number of degrees of freedom) makes it essential to use statistical methods that enable the transition from the microscopic to the macroscopic, where only the mean values of physical quantities, and possibly their fluctuations, are observed.

Classical or phenomenological thermodynamics and statistical thermodynamics are different ways of investigating different data; both aim to establish thermodynamic functions. For definitions of thermodynamic quantities, please refer to the other articles in this section, in particular "Chemical thermodynamics".