Thermodynamics

Laws of Thermodynamics

• Zeroth Law of Thermodynamics ("You have to play the game.")
• If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other
• Two bodies are in thermal equilibrium if there is no net flow of thermal energy between them when they are in thermal contact
• First Law of Thermodynamics ("You can't win.")
• In a closed system, \(\triangle U = Q - W\)
• \(\triangle U\): Change in the internal energy
• \(Q\): Amount of heat supplied to the system
• \(W\): Amount of work done by the system on its surroundings
• Second Law of Thermodynamics ("You can't break even.")
• In a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic systems increases.
• Maxwell's demon does not violate the second law
• Third Law of Thermodynamics ("You can't even quit the game.")
• The entropy of a system approaches a constant value as the temperature approaches absolute zero.

Work Done by Gas

• \(W = \int_{V_1}^{V_2} P dV\)
• Work done = Area under the curve in a \(P\)-\(V\) graph

Thermodynamics Processes of Ideal Gas

• Isobaric Process
• \(\triangle P=0\)
• Isochoric Process (Isovolumetric Process)
• \(\triangle V=0\), thus \(W=0\)
• Isothermal Process
• \(\triangle T=0\); \(\triangle U=0\)
• \(PV\) (\(=nRT\)) remains constant
• Adiabatic Process
• \(Q=0\)