entropy

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entropy

 [en´trŏ-pe]
1. in thermodynamics, a measure of the part of the internal energy of a system that is unavailable to do work. In any spontaneous process, such as the flow of heat from a hot region to a cold region, entropy always increases.
2. the tendency of a system to move toward randomness.
3. in information theory, the negative of information, a measure of the disorder or randomness in a physical system. The theory of statistical mechanics proves that this concept is equivalent to entropy as defined in thermodynamics.
4. diminished capacity for spontaneous change, as occurs in the psyche in aging.

en·tro·py (S),

(en'trŏ-pē),
That fraction of heat (energy) content not available for the performance of work, usually because (in a chemical reaction) it has been used to increase the random motion of the atoms or molecules in the system; thus, entropy is a measure of randomness or disorder. Entropy occurs in the Gibbs free energy (G) equation: ΔG = ΔH - TΔSH, change in enthalpy or heat content; T, absolute temperature; ΔS, change in entropy; ΔG, change in Gibbs free energy).
See also: second law of thermodynamics.
[G. entropia, a turning toward]

en·tro·py

(S) (en'trŏ-pē)
That fraction of heat (energy) content not available for the performance of work, usually because (in a chemical reaction) it has been used to increase the random motion of the atoms or molecules in the system; thus, a measure of randomness or disorder.
[G. entropia, a turning toward]

entropy

the amount of disorder or the degree of randomness of a system. For example, when a protein is denatured by heat (see DENATURATION), the molecule (which has a definite shape) uncoils and takes up a random shape, producing a large change in entropy.
References in periodicals archive ?
The magnetic field, entropy changes, and heat transfer dependence on magnet array geometry were observed.
In addition to large magnetic entropy changes, large values of relative cooling power (RCP) are essential for magnetic refrigeration.
In order to assess the magnetic entropy changes ([DELTA][S.sub.M]) in the [Mn.sub.5-x][Fe.sub.x][Ge.sub.3] compounds, isothermal M(H) data was collected at multiple temperatures in the vicinity of the samples' [T.sub.C].
The entropy change ([DELTA]S) is a measure of disorder in the human physiological system caused by heat transfer due to imbalance in the internal physiology as a result of imposed psychological stress and is equated to entropy damage ([DELTA][S.sub.D]).
The entropy change depicted in Figures 6 and 7 can be expressed in terms of pressures ratio and compression rate as follows [22]:
At very low temperatures, the energy of the system changes very slowly, even though the entropy changes enormously.
The kinetic parameters, such as order of the degradation (n), energy of activation (E), frequency factor (A) and entropy change ([DELTA]S) for each step are reported in Tables 3 to 5.
Unlike gadolinium, most G[d.sub.5]S[i.sub.4-x][Ge.sub.x] compounds are FOMT materials, and the entropy change with magnetization is larger than that of gadolinium but is also much sharper, occurring over a narrower temperature range.
If work inputs are sufficiently large, the rate of total entropy change can even become negative, indicating greater organizational productive capability.
They go on to claim that they have established a novel connection between the asymmetric knowledge we have of past and future, on the one hand, and entropy change, on the other.
The initial work was done by Jacobson who showed that the gravitational Einstein equation can be derived from the relation between the horizon area and entropy, together with the Clausius relation [delta]Q = T[delta]S (where [delta]Q, T, and [delta]S represent the change in energy, temperature, and entropy change o the system, respectively) [33].