Prof. Leonard Susskind presents the mathematical definition of pressure using the Helmholtz free energy, and then derives the famous equation of state for an ideal gas: pV = NkT. Recorded on April 29, 2013.

1. Entropy and Conservation of Information
2. Temperature
3. Maximizing Entropy
4. The Boltzmann Distribution
5. Pressure of an Ideal Gas and Fluctuations
6. Weakly-interacting Gases, Heat, and Work
7. Entropy vs. Reversibility
8. Entropy, reversibility, and magnetism
9. The Ising model
10. Liquid-gas phase transition

Statistical mechanics is a branch of physics that applies probability theory to the study of the thermodynamic behavior of systems composed of a large number of particles. Statistical mechanics provides a framework for relating the microscopic properties of individual atoms and molecules to the macroscopic bulk properties of materials that can be observed in everyday life. Thus it explains thermodynamics as a result of the classical and quantum-mechanical descriptions of statistics and mechanics at the microscopic level.