Entropy universe

Ions or molecules flowing down their concentration gradients is one aspect of a very general statement known as the Second Law of Thermodynamics. The Second Law is a mathematical statement to the effect that all real processes increase the disorder, captured in a quantity known as entropy, of the universe. Entropy is a measure of disorder or randomness and may be thought of as negative information. 

The latter statement evokes the image of inexorable entropy increase as the ultimate progress variable of the universe. Entropy presumably evolves toward an eventual equilibrium limit that marks the end of spontaneous change in our universe heat death (Warmetod). Sidebar 4.9 warns against common conceptual errors that result from superficial application of the entropy-increase principle (4.48). 

Reactions at equilibrium have achieved Equilibrium is the point in a reaction where the universe has achieved maximum en-ritaximum universal entropy. tropy. A thermodynamically reversible reaction is one that remains infinitely close... 

AHsysk.lu under these conditions, we have ASsll,Tmindings = -AHsyptmi/T. Therefore, in a closed system capable of doing only PV work, and at constant temperature and pressure, equilibrium is achieved by maximizing universal entropy via the equation ... 

From the scientific definition point of view, there is a slight difference between our continuum thermodynamics definition of the Second Law and its statistical mechanical version so that the continuum thermodynamics definition of the Second Law states that an observation of decreased universal entropy is impossible in isolated systems however the statistical mechanical definition says that an observation of universal increased entropy is not probable. 

G is the famous Ciihbs free energy. Tt follows that fi) and fii) are equivalent forms of the second law and an increase in the universal entropy corresponds to a decrease in the free energy oj the system. Therefore changes in a sy.stem can only occur if. as a result, the free energy of the system decreases. 

Equation (A2.1.21) includes, as a special case, the statement dS > 0 for adiabatic processes (for which Dq = 0) and, a fortiori, the same statement about processes that may occur in an isolated system (Dq = T)w = 0). If the universe is an isolated system (an assumption that, however plausible, is not yet subject to experimental verification), the first and second laws lead to the famous statement of Clausius The energy of the universe is constant the entropy of the universe tends always toward a maximum. ... 

Morowitz, H.J. (1993) Entropy and the Magic Flute (Oxford University Press, Oxford)... 

Georgescu-Roegen, N. (1971). The Entropy and the Economic Process. Cambridge, MA Harvard University Press. 

Thus, in adiabatic processes the entropy of a system must always increase or remain constant. In words, the second law of thermodynamics states that the entropy of a system that undergoes an adiabatic process can never decrease. Notice that for the system plus the surroundings, that is, the universe, all processes are adiabatic since there are no surroundings, hence in the universe the entropy can never decrease. Thus, the first law deals with the conservation of energy in any type of process, while the sec-... 

Because the gas in the Carnot cycle starts and ends at the same state, the system s entropy does not change during a cycle. Now apply the second law to the universe for the case of the Carnot cycle. Because the processes are reversible, the entropy of the universe does not change by Equation 2b. This can be written ... 

Equation 5, DS = 0 = —Qn/T , which is impossible since Q = W is not zero and this implies the entropy of the universe would decrease. 

This leads to what is called the Clausius form of the second law of thermodynamics. No processes are possible whose only result is the removal of energy from one reservoir and its absorption by another reservoir at a higher temperature. On the other hand, if energy flows from the hot reservoir to the cold reservoir with no other changes in the universe, then the same arguments can be used to show that the entropy increases, nr remains constant for reversible processes. Therefore, such energy flows, which arc vciy familiar, are in agreement with the laws of thermodynamics. 

Ieff90] LefF, H.S, and A.F.Rex, editors. Maxwell s Demon entropy, information, computing, Princeton University Press, 1990. 

Thermodynamic, second law The entropy of the universe increases in a spontaneous process and remains unchanged in a reversible process. It can never decrease. 

If the system is not isolated, its entropy may either increase or decrease. Thus, if a mass of gas is compressed in a cylinder impervious to heat, its entropy increases, but if heat is allowed to pass out into a medium, the entropy of the gas may decrease. By including the"gas and medium in a larger isolated system, we can apply (10) of 45, and hence show Jhat the medium gains more entropy than the gas loses. An extended assimilation of this kind shows that, if every body affected in a change is taken into account, the entropy of the whole must increase by reason of irreversible changes occurring in it. This is evidently what Clausius (1854) had in mind in the formulation of his famous aphorism The entropy of the universe strives towards a maximum. The word universe is to be understood in the sense of an ultimately isolated system. 

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