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## The Laws of Thermodynamics ### Zeroth Law If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. * Establishes temperature as a fundamental property that can be used to determine if systems are in thermal equilibrium. *...

## The Laws of Thermodynamics ### Zeroth Law If two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. * Establishes temperature as a fundamental property that can be used to determine if systems are in thermal equilibrium. * If A = C and B = C, then A = B ### First Law The increase in the internal energy of a system is equal to the amount of heat added to the system minus the work done by the system. * Deals with the conservation of energy. * $\Delta U = Q - W$ * $\Delta U$: Change in internal energy * $Q$: Heat added to the system * $W$: Work done by the system ### Second Law The total entropy of an isolated system can only increase over time. * Deals with the direction of natural processes. * $\Delta S \geq 0$ * $\Delta S$: Change in entropy * Heat cannot spontaneously flow from a cold body to a hot body. * No heat engine can be more efficient than a Carnot engine operating between the same two temperatures. ### Third Law As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum or zero value. * Deals with the behavior of systems at very low temperatures. * $lim_{T \to 0} S = S_0$ * $S_0$: Minimum entropy, which is typically zero for a perfect crystalline substance. * It is impossible to reach absolute zero in a finite number of steps. ### Enthalpy A thermodynamic property of a system, is the sum of the internal energy and the product of its pressure and volume. * $H = U + PV$ * $H$: Enthalpy * $U$: Internal energy * $P$: Pressure * $V$: Volume ### Gibbs Free Energy A thermodynamic potential that measures the amount of energy available in a thermodynamic system to perform useful work at a constant temperature and pressure. * $G = H - TS = U + PV - TS$ * $G$: Gibbs Free Energy * $H$: Enthalpy * $T$: Absolute Temperature * $S$: Entropy * $U$: Internal energy * $P$: Pressure * $V$: Volume * $\Delta G < 0$: Spontaneous process * $\Delta G > 0$: Non-spontaneous process * $\Delta G = 0$: Equilibrium