PX284 - B0 - approaches to thermal physics

thermodynamics

• assumes a unique normal state called 'thermal equilibrium'
• states four laws relating pressure, temperature, internal energy, entropy, and volume
• the laws are empirical and justified experimentally

statistical mechanics

• defines 'thermal equilibrium' and entropy in terms of microscopic probabilities
• gives the probability of a particular state
• determines measurable properties using averaged over states