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# Thermodynamics ## Zeroth Law of Thermodynamics If objects A and B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each other. ## First Law of Thermodynamics The change in internal energy of a system is equal to the heat added to the sys...

# Thermodynamics ## Zeroth Law of Thermodynamics If objects A and B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each other. ## First Law of Thermodynamics The change in internal energy of a system is equal to the heat added to the system minus the work done by the system: $\Delta U = Q - W$ ## Second Law of Thermodynamics ### Entropy Statement The total entropy of an isolated system can never decrease over time. ### Kelvin-Planck Statement It is impossible to construct a heat engine that operates in a cycle and performs work while exchanging heat with a single reservoir. ### Clausius Statement It is impossible to construct a device that operates in a cycle and transfers heat from a cold reservoir to a hot reservoir without work input. ## Third Law of Thermodynamics As the temperature of a system approaches absolute zero, the entropy of the system approaches a minimum or zero value. ## Thermodynamic Processes ### Isobaric Constant pressure. $W = P\Delta V$ ### Isochoric Constant volume. $W = 0$ $\Delta U = Q$ ### Isothermal Constant temperature. $\Delta U = 0$ $Q = W$ ### Adiabatic No heat exchange. $Q = 0$ $\Delta U = -W$ ## Heat Engines A heat engine is a device that converts thermal energy into mechanical work. $\eta = \frac{W}{Q_H} = 1 - \frac{Q_C}{Q_H}$ ## Refrigerators and Heat Pumps A refrigerator is a device that transfers heat from a cold reservoir to a hot reservoir by using work input. $COP = \frac{Q_C}{W}$ A heat pump is a device that transfers heat from a cold reservoir to a hot reservoir by using work input. $COP = \frac{Q_H}{W}$ ## Ideal Gas Law $PV = nRT$ Where: - P is the pressure - V is the volume - n is the number of moles - R is the ideal gas constant - T is the temperature ## Kinetic Theory of Gases ### Average Translational Kinetic Energy $KE_{avg} = \frac{3}{2}kT$ Where: - k is the Boltzmann constant - T is the temperature ### Root Mean Square (RMS) Speed $v_{rms} = \sqrt{\frac{3kT}{m}} = \sqrt{\frac{3RT}{M}}$ Where: - m is the mass of one molecule - M is the molar mass ## Heat Transfer ### Conduction The transfer of heat through a material by direct contact. $Q = \frac{kA(T_H - T_C)t}{L}$ Where: - k is the thermal conductivity - A is the area - L is the thickness - t is the time ### Convection The transfer of heat by the movement of a fluid. ### Radiation The transfer of heat by electromagnetic waves. $Q = \epsilon \sigma A T^4 t$ Where: - $\epsilon$ is the emissivity - $\sigma$ is the Stefan-Boltzmann constant - A is the area - T is the temperature - t is the time