Thermodynamics (2023/2024) (S01+S02) Pr. BOURSAS Abdelhakim

     This course entitled classical thermodynamics is intended for first-year common core students of the Faculty of Technology. It is drawn up in accordance with the framework established by the Ministry of Higher Education and Scientific Research (MESRS) of the People's Democratic Republic of Algeria.

     The course is spread over seven chapters. The first covers basic concepts and definitions, as well as terminology frequently used in thermodynamics. Towards the end of this chapter we presented the ideal gas model as an example of thermodynamic systems and the classical laws governing its behavior and at the end a synthesis of these laws which highlights the equation of state of the ideal gas PV = nRT, Some examples of the equations of state of real gases are cited for comparison and the meaning of the parameters appearing there, characterizing each real gas.

     The second chapter is devoted to thermometry, a field which concerns the identification or measurement of temperature according to the thermometric scale used. There the so-called “Zero” principle in thermodynamics is stated. It is mainly the basis of the temperature measurement technique. But its interest is not limited only to the field of thermometry. Its importance is clearer in the study of internal thermal balances of thermodynamic systems and possibly with the external environment with which they interact. In this chapter the temperature measurement scales are reviewed. Particular emphasis is placed on linear scales and more particularly those called centesimals. obviously to finish, some types of thermometers and their operating principles are explained. A particular type of thermometer called a pyrometer, whose operating principle is different, is mentioned towards the end.

Chapter three covers the first principle in thermodynamics or the principle of conservation of energy. Firstly, two transfer quantities are highlighted in this case; work and heat, which are described separately as two forms of energy, the difference between which lies in their impact on the system. Subsequently the first principle is stated by admitting the existence of a certain state function called internal energy and denoted U, the variation of which is due to the exchange of work and heat. Some consequences are immediately drawn from this principle as that of an isolated system. More particularly a new state function called enthalpy and denoted H is introduced to study monobaric or isobaric transformations. Later in this chapter, the application of the first law to the ideal gas model revealed two ideal gas laws; Joule's first and second law. These two laws allowed an easy calculation of the energy quantities of the ideal gas during simple transformations.

     Chapter four is devoted to the application of the first principle to chemical reactions commonly called thermochemistry. This is a field concerned with the calculation of the heat accompanying chemical reactions, referred to as heat of reaction. We mainly distinguish between them types of heat; the heats at constant volume and the heats at constant pressure, which are calculated by the variation of the internal energy U and the variation of the enthalpy H respectively. It is a very valuable tool as it allows us to calculate the heat of reaction without having to actually carry out the reaction in question, while basing it on a set of tabulated values called enthalpies of formation and/or heats of formation. reactions calculated or measured previously.
     If the first principle allows us to trace an energy balance at the end of a given transformation, it cannot predict the sense of spontaneity (the sense of irreversibility) of this transformation. Precisely and within the framework of the first principle both directions of the transformation are possible as long as the energy balance is well verified. Practically it has been observed that a spontaneous transformation in one direction cannot take place in the other direction. This is where the second law of thermodynamics comes in (subject of the fifth chapter). This principle provides the sense of spontaneity of a transformation, Therefore the impossibility of the other. To do this we introduced a new concept that of "Entropy", denoted S. A spontaneous transformation is always accompanied by an increase in entropy until it reaches its maximum value. It has been statistically proven that entropy is proportional to the disorder in the system, which means that the disorder will be maximum at the end of the spontaneous transformation. A mathematical formulation is highlighted to express the variation of entropy during any transformation (reversible or irreversible). Detailed calculations on entropy are carried out for the case of an ideal gas undergoing simple transformations (reversible or irreversible)
     The third principle in thermodynamics, presented in chapter six, also called Nernst's theorem, after the Nobel Prize winner who discovered it in 1906, is stated as follows: "The entropy of any system can always be taken equal to zero at the temperature of absolute zero". It follows directly from this that the variation in molar entropy of a uniform monophasic substance during an isobaric transformation which changes its temperature from T0 to T can be calculated by:
                                                                                                      
     Therefore the absolute entropy of a uniform monophasic substance can be calculated for a given temperature, something which is not possible for the internal energy U.
     In the last chapter (chapter VII) chemical equilibria in the gas phase are studied. Two state functions are used for this purpose; Helmholtz and Gibbs functions