Entropy of universe

And the surroundings and the system of steam together gain the same amount of entropy. The entropy of universe thus remains constant. 

By similar examples, it can be proved that in an irreversible process (or a real process), the system under consideration may lose or gain entropy, but the entropy of universe always increases ... 

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. ... 

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. 

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. 

Phase changes are examples of (c). In order to melt a mole of ice in contact with air at 298.15 K, heat must flow into the system from the air. The increase in entropy of the system is 22.00 J K-1 - mol-1. The heat leaving the air decreases its entropy by 20.15 J K-1 mol-1. The net change in the universe is once again positive ... 

Adiabatic processes are examples of (d). If a mole of ideal gas is allowed to expand adiabatically into an evacuated bulb to twice its initial volume, the entropy of the gas increases by 5.76 J K-1 mol-1. No entropy change occurs in the surroundings, since there is no exchange of heat. Hence, 5.76 J K-1 mol-1 is the net increase in entropy in the universe. 

Entropy is an important concept in chemistry because we can use it to predict the natural direction of a reaction. However, not only does the entropy of the reaction system change as reactants form products, but so too does the entropy of the surroundings as the heat produced or absorbed by the reaction enters or leaves them. Both the entropy change of the system and that of the surroundings affect the direction of a reaction, because both contribute to the entropy of the universe. We explore the contribution of the system in this section and the contribution of the surroundings in the next section. 

The first law of thermodynamics states that energy is neither created nor destroyed (thus, The energy of the universe is constant ). A consequence of the second law of thermodynamics is that entropy of the universe increases for all spontaneous, that is, naturally occurring, processes (and therefore, the entropy of the universe increases toward a maximum ). 

The author thanks Professor Slobodan Zumer, Department of Physics, University of Ljubljana, for pointing out the effect of the entropy of out-of-layer fluctuations on the I-Sm transition. 

Figure 4.2 Schematic representation of a crystallization process. Each solvated ion, here Na+, releases six waters of solvation while incorporating into its crystal lattice. The overall entropy of the thermodynamic universe increases by this means...

The simplest rules of thermodynamics suggest that energy must be expended to do work— You cannot get something for nothing, and that even if work is done some energy is forever lost to useful work— You cannot even get what you paid for . And that this entropy effect is such that the entropy of the universe is forever driving toward a maximum— Nature spontaneously falls into a mess Humor aside, the consequence is that any narrow packet as described above will spread over space in an attempt to make the local and universal mole fraction of A, B or C. .. the same everywhere. 

The second law of thermodynamics involves a term called entropy. Entropy is a measure of the degree that energy disperses from a localized state to one that is more widely spread out. We may also think of entropy (S) as a measure of the disorder of a system. The second law of thermodynamics states that all processes that occur spontaneously move in the direction of an increase in entropy of the universe (system + surroundings). For a reversible process, a system at equilibrium, ASuniverse = 0. We can state this as ... 

According to this second law, the entropy of the universe is continually increasing. The third law of thermodynamics states that for a pure crystalline substance at 0 K the entropy is zero. 

The first law of thermodynamics states that the total energy of the universe is constant. The second law of thermodynamics states, that in all spontaneous processes, the entropy of the system increases. Entropy is a measure of the dispersion of energy from a localized one to a more disperse one. It can be... 

Second Law of Thermodynamics The Second Law of Thermodynamics states that all processes that occur spontaneously move in the direction of an increase in entropy of the universe (system + surroundings). 

DR. ALBERT HAIM (State University of New York at Stony Brook) I guess you know as well as I do, and as most people do, how difficult it is to find evidence for a mechanism, whether it is dissociative or associative or falls in between. You have measured volumes of activation, and have obtained information from them. You seem to be very certain as to the conclusions that you can draw from the various numbers which you obtained. Suppose that one were a little skeptical about the value of these numbers and wanted to ask how they compared with other parameters that one can measure in the same systems, such as entropies of activation, or energies of activation. From the point of view of volumes of activation, is a picture obtained which is consistent with what one may derive from other measurements ... 

---