Comprehensive notes for Chapter 6 Heat and Thermodynamics. Covers Laws of Thermodynamics, Entropy, Heat Engines, Carnot Cycle, and Gas Laws.
Assumptions: Gas consists of large number of tiny particles in constant random motion. Collisions are perfectly elastic. No intermolecular forces. Volume of molecules is negligible compared to gas volume.
Pressure: Due to collisions with container walls.
Ideal Gas Equation: PV = nRT or PV = Nk_BT (where k_B is Boltzmann constant).
Statement of Conservation of Energy.
Q = ΔU + W
Isothermal: Constant Temperature (ΔT=0, ΔU=0). PV = Constant (Boyle's Law). Q = W.
Adiabatic: No Heat Exchange (Q=0). PV^γ = Constant. Work is done at expense of Internal Energy (W = -ΔU). Curve is steeper than Isotherm.
Isobaric: Constant Pressure. W = PΔV.
Isochoric: Constant Volume. W = 0.
Kelvin-Planck Statement: Impossible to construct a heat engine that absorbs heat from a single reservoir and converts it entirely into work. (Efficiency < 100%).
Clausius Statement: Impossible for heat to flow from cold to hot body without external work (Refrigerator).
Carnot Cycle: Ideal reversible cycle with four steps: Isothermal Expansion, Adiabatic Expansion, Isothermal Compression, Adiabatic Compression.
Efficiency: η = 1 - (T_cold / T_hot). Depends only on temperatures of source and sink.
Entropy (S): Measure of disorder. ΔS = ΔQ/T (Reversible). In all natural (irreversible) processes, entropy of the universe increases.