This chapter is about thermodynamics, or statistical mechanics, which explains macroscopic features of the world in terms of the motion of vast numbers of particles on the atomic scale. It discusses how macroscopic variables such as temperature and entropy were originally introduced, before presenting modern definitions of temperatures and entropy and the Laws of Thermodynamics. Alternative thermodynamic variables, including enthalpy and the Gibbs free energy, are defined and the Gibbs distribution is explained. The Maxwell distribution is derived. The chemical potential is introduced and the pressure and heat capacity of an electron gas is calculated, The Fermi–Dirac and Bose–Einstein functions are derived. Bose–Einstein condensation is explained. Black body radiation is discussed and the Planck formula is derived. Lasers are explained. Spin systems are used to model magnetization. Phase transitions are briefly discussed. Hawking radiation and the thermodynamics of black holes is explained.
Bose Einstein condensation in a magnetic double-well potential
