Term | Definition |
spontaneous process | a process that is capable of proceeding in a given direction, as written or described, without needing to be driven by an outside source of energy. |
reversible process | a process that can go back and forth between states along exactly the same path;a system at equilibrium is reversible if equilibrium can be shifted by an infinitesimal modification of a variable such as temperature |
irreversible process | a process that is not reversible; and as a result, some of its potential for accomplishing work is dissipated as heat. any spontaneous process is irreversible in practice |
isothermal process | one that occurs at constant temperature |
second law of thermodynamics | when a process occurs spontaneously in one direction, it is non-spontaneous in the reverse direction.
in any spontaneous process the entropy of the universe increases |
entropy | a thermodynamic function associated with the number of different equivalent energy states or spatial arrangements in which a system may be found |
translational motion | movement in which an entire molecule moves in a definite direction |
vibrational motion | movement of the atoms within a molecule in which they move periodically toward and away from one another |
rotational motion | movement of a molecule as though it is spinning like a top |
microstate | the state of a system at a particular instant; one of many possible states of the system |
third law of thermodynamics | a law stating that the entropy of a pure, crystalline solid at absolute zero temperature is zero |
standard molar entropy (S degree) | the entropy value for a mole of a substance in its standard state |
Gibbs free energy | a thermodynamic state function that combines enthalpy and entropy; in the form G= H - TS |
standard free energies of formation ( delta G degree sub f) | the change in free energy associated with the formation of a substance from its elements under standard conditions |