An Introduction to Thermodynamics and the First Law

Abstract

The introductory chapter presents the basic concepts of classical thermodynamics such as system type (open, closed and isolated), two of the state functions (internal energy and the help function, enthalpy) and their temperature derivatives (heat capacities at constant volume and constant pressure), energy transfer quantities (e.g. work and heat), the important concepts reversibility and irreversibility, thermo-chemistry (endo- and exothermal processes) and the Kirchhoff law which enables the calculation of the temperature dependence of the enthalpy change associated with phase transitions and chemical reactions. The first law of thermodynamics is, however, the main theme. This law states that the energy of the universe is constant. This chapter presents examples showing the two ‘faces’ of the internal energy, the potential energy and the kinetic energy. The first law is in many examples applied to ideal gases, because of the simplicity of the pressure-volume-temperature relationship, the ideal gas law.