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Development of a thermal equilibrium in a closed system over time through a heat flow that levels out temperature differences. Two physical systems are in thermal equilibrium if there is no net flow of thermal energy between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics. A ...
His system is, however, closed with respect to transfer of matter. He writes: "In general, the approach to thermodynamic equilibrium will involve both thermal and work-like interactions with the surroundings." He distinguishes such thermodynamic equilibrium from thermal equilibrium, in which only thermal contact is mediating transfer of energy ...
If it is defined that a thermodynamic system is in thermal equilibrium with itself (i.e., thermal equilibrium is reflexive), then the zeroth law may be stated as follows: If a body C, be in thermal equilibrium with two other bodies, A and B, then A and B are in thermal equilibrium with one another. [8]
Thus, a negative value of the change in free energy is a necessary condition for a process to be spontaneous; this is the most useful form of the second law of thermodynamics in chemistry. In chemical equilibrium at constant T and p without electrical work, dG = 0.
At thermal equilibrium the energy entropy is equal to the von Neumann entropy: =. S v n {\displaystyle S_{\rm {vn}}} is invariant to a unitary transformation changing the state. The Von Neumann entropy S v n {\displaystyle S_{\rm {vn}}} is additive only for a system state that is composed of a tensor product of its subsystems:
Thermalisation, thermal equilibrium, and temperature are therefore important fundamental concepts within statistical physics, statistical mechanics, and thermodynamics; all of which are a basis for many other specific fields of scientific understanding and engineering application. Examples of thermalisation include:
In solution chemistry and biochemistry, the Gibbs free energy decrease (∂G/∂ξ, in molar units, denoted cryptically by ΔG) is commonly used as a surrogate for (−T times) the global entropy produced by spontaneous chemical reactions in situations where no work is being done; or at least no "useful" work; i.e., other than perhaps ± P dV.
To maintain this constant entropy, any exchange of work energy with the environment must therefore be quasi-static in nature in order to ensure that the system remains essentially at equilibrium during the process. [1] The opposite of a thermally isolated system is a thermally open system, which allows the transfer of heat energy and entropy.