Thermodynamics is the foundation on which the science of physical chemistry is built, and statistical thermodynamics provides the fundamental, molecular-level basis for the ideas of thermodynamics. This course will focus on the ability of statistical thermodynamics to employ simple physical models, along with some inspired mathematics, to predict the behavior of atoms and molecules (referred to as, "the unreasonable effectiveness of unrealistic simplifications"). The concept of entropy will be a unifying theme throughout the course, and, given its central role, time will be devoted to developing a rigorous mathematical model of entropy through the use of probability and multi-variable calculus. The more traditional topics of thermodynamics will be presented relatively quickly. The first and second laws of thermodynamics will be explored; the fundamental equations of thermodynamics, as differential equations, will be used to define the properties of temperature, pressure and chemical potential; and the concept of free energy (and its importance in describing equilibrium) will be developed. The Boltzmann distribution law (and the partition function) will be derived and then used, along with simple physical models, to compute thermodynamic and physical properties of systems at equilibrium. Following a brief look at quantum theory and statistical mechanics, the equilibrium constant expression will be derived (by employing the partition function) and values for gas-phase chemical equilibrium constants will be computed and compared to empirical values. Finally, lattice models will be used to explore properties of liquids, liquid/vapor equilibrium and solutions. There will be some experimental work, allowing students the opportunity to study an actual system and use the simple models, and mathematics, of statistical thermodynamics to investigate its physical and/or chemical behavior.