Classical or equilibrium thermodynamics: basic conceptual aspects.

Antonio Braz de Pádua, Cléia Guiotti de Pádua, João Lucas Correia Silva, Ricardo Spagnuolo Martins, Felipe Barreiro Postali, Luiz Augusto Calvo Tiritan


The Classical or Equilibrium Thermodynamics is one of the most consolidated fields of Physics. It is synthesized by a well-known and self coherent knowledge structure. The essence of the Classical Thermodynamics theoretical structure consists of a set of natural laws that rule the macroscopic physical systems behavior. These laws were formulated based on observations generalizations and are mostly independent of any hypotheses concerning the microscopic nature of the matter. In general, the approaches established for the Classical Thermodynamics follow one of the following alternatives: the historical approach that describes chronologically the evolution of ideas, concepts and facts, and the postulational approach in which postulates are formulated but are not demonstrated a priori but can be confirmed a posteriori. In this work, a brief review of the pre-classical historical approach conceptual evolution is elaborated, from the beginning of the seventeenth century to the middle of the nineteenth century. As for this, the following themes are dealt with in an evolutionary and phenomenological way: heat nature, thermometry, calorimetry, Carnot’s heat engine, heat mechanical equivalent and the first and second laws. The Zeroth law that was formulated afterwards is included in the discussion.


Thermodynamics laws; Temperature; Thermal equilibrium; Heat; Calorific; Heat engine; Carnot’s Cycle; Internal energy; Mechanical work; Heat mechanical equivalent; Entropy.


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