Thermodynamics

Energy conservation: heat in equals internal-energy change plus work done.

Specific heats at constant P vs V; the Mayer relation.

Constant-temperature gas process; PV = const.

No heat exchange; PV^γ = const along the path.

Heat flows spontaneously only from hot to cold (Kelvin–Planck / Clausius).

Engine vs refrigerator vs heat pump and their performance coefficients.