The study of Thermodynamics is not a new discipline in physics. For most of its history, Thermodynamics and its postulates and equations had little theoretical basis but were accepted because they were well verified by experiment. However, with the advent of quantum mechanics in the early 20th Century, quantum-level explanations were formulated that could explain the macroscopic behaviors of thermal systems.
For this reason, we begin our treatment of Thermodynamics with a look at the quantum basis for the statistics that govern macroscopic behavior. Do not fear if you don't understand Quantum Mechanics; we won't focus on that aspect of the physics but instead will utilize the quantum way of thinking about the state of a system. We will examine the Fundamental Assumption of Thermodynamics and investigate its application to probability via the multiplicity function. We will close our quantum inspection by learning about the average value of a variable in an ensemble.
We delve into the heart of Thermodynamicsm, then, by defining the entropy and temperature of a system, making sure to distinguish between the conventional and fundamental definitions of these two variables. We'll close by looking at the 3 Laws of Thermodynamics that govern our approach to the subject.