Topic overview

Start with the big picture

A microstate specifies how particles occupy defined quantum states, while a macrostate reflects their collective behavior. The number of microstates, W, links to entropy through the Boltzmann relation. At thermal equilibrium, the Boltzmann distribution describes how populations vary across energy levels, with degeneracy affecting occupancy. The canonical partition function gathers contributions from accessible states and connects molecular statistics with thermodynamic quantities. The topic also introduces equipartition, Maxwell–Boltzmann speeds, and distinct treatments of translational, rotational, and vibrational motion. Statistical ensembles describe systems under different fixed conditions, and residual entropy illustrates how multiple ground-state arrangements can remain. Together, these ideas establish a foundation for interpreting molecular structure and change statistically.