Knowra Thermodynamic potential Thermodynamic potential A state function that summarizes a system’s thermodynamic state and helps determine equilibrium under specified constraints. Internal energy, Helmholtz free energy, enthalpy, and Gibbs free energy are examples.
Thermodynamic state : The condition of a thermodynamic system specified by macroscopic variables such as temperature, pressure, and volume. A potential assigns a value to each state of the system.
Fundamental thermodynamic relation : An equation expressing the differential of a system’s internal energy in terms of entropy, volume, particle number, and conjugate variables. It provides the starting point for deriving other thermodynamic potentials.
Gibbs free energy of formation : The Gibbs free-energy change for forming one mole of a compound from its elements in their reference states. Formation values let chemists calculate reaction spontaneity at fixed temperature and pressure.
Heat : Energy transferred between systems because of a temperature difference. Heat is path-dependent energy transfer, not a state-function potential.
State function : A property whose value depends only on a system’s state, not on the path taken to reach it. Thermodynamic potentials are state functions, unlike heat and work.
Internal energy : The energy contained within a system, excluding its motion and position as a whole. It is the basic energy function from which the standard potentials are constructed.
Chemical equilibrium : A state in which forward and reverse chemical reactions proceed at equal rates, leaving composition macroscopically constant. Reaction equilibrium corresponds to a minimum of Gibbs free energy under suitable conditions.
Work (thermodynamics) : Energy transferred through organized macroscopic forces acting over a displacement or change. Work depends on the process path, unlike thermodynamic potentials.
Thermodynamic equilibrium : A condition in which a system has no macroscopic driving forces for change under its constraints. Equilibrium is identified by extremizing the appropriate potential.
Helmholtz free energy : The thermodynamic potential defined as internal energy minus temperature times entropy. It is minimized at equilibrium when temperature and volume are fixed.
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