Spontaneous processes entropy increase

Gibbs criteria of equilibrium, of course, are in agreement with the second law of thermodynamics, which gives evidence of the variation of entropy in spontaneous processes (entropy increase) but gives no explicit evidence on the state of equilibrium itself. 

Entropy is a measure of disorder according to the second law of thermodynamics, the entropy of an isolated system increases in any spontaneous process. Entropy is a state function. 

The entropy of a system can decrease during a spontaneous process or increase during a nonspontaneous process, depending on the accompanying AS j.j.. If AS yg is negative... 

The degree of disorder of a system is measured by the state function called entropy (S). The more disordered a system is, the greater is its entropy value. According to the second law, the entropy change of the universe is positive for every spontaneous process. The increase may take place in any part of the universe (A.S sys or A.S sun) ... 

Another statement of the second law is this in any spontaneous process, the entropy of the Universe increases (AS. > 0). This statement is general, and it applies to any set of conditions. It is not confined to the special case of constant temperature and pressure, as is the statement that the free energy decreases in a spontaneous process. Entropy changes are particularly important in determining the energetics of protein folding. 

The relationship between entropy change and spontaneity can be expressed through a basic principle of nature known as the second law of thermodynamics. One way to state this law is to say that in a spontaneous process, there is a net increase in entropy, taking into account both system and surroundings. That is,... 

Second law of thermodynamics A basic law of nature, one form of which states that all spontaneous processes occur with an increase in entropy, 457 Second order reaction A reaction whose rate depends on the second power of reactant concentration, 289,317q gas-phase, 300t... 

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

In any spontaneous process, the total entropy increases A S tgta] > 0. ... 

In thermodynamics, entropy enjoys the status as an infallible criterion of spontaneity. The concept of entropy could be used to determine whether or not a given process would take place spontaneously. It has been found that in a natural or spontaneous process there would be an increase in the entropy of the system. This is the most general criterion of spontaneity that thermodynamics offers however, to use this concept one must consider the entropy change in a process under the condition of constant volume and internal energy. Though infallible, entropy is thus not a very convenient criterion. There have, therefore, been attempts to find more suitable thermodynamic functions that would be of greater practical... 

Notice that dephasing of the transverse magnetization does not affect Mz a T2 process involves no energy transfer but, being a spontaneous process, does involve an increase in the entropy of the spin system. 

Hence, for an isolated system, the entropy of the system alone must increase when a spontaneous process takes place. The second law identifies the spontaneous changes, but in terms of both the system and the surroundings. However, it is possible to consider the specific system only. This is the topic of the next section. 

The Helmholtz and Gibbs energies on the other hand involve constant temperature and volume and constant temperature and pressure, respectively. Most experiments are done at constant Tandp, and most simulations at constant Tand V. Thus, we have now defined two functions of great practical use. In a spontaneous process at constant p and T or constant p and V, the Gibbs or Helmholtz energies, respectively, of the system decrease. These are, however, only other measures of the second law and imply that the total entropy of the system and the surroundings increases. 

We now introduce the second law of thermodynamics a physicochemical process only occurs spontaneously if accompanied by an increase in the entropy S. By corollary, a non-spontaneous process - one that we can force to occur by externally adding energy - would proceed concurrently with a decrease in the energetic disorder. 

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... 

The Second Law of Thermodynamics states that all spontaneous processes move in a way that increases the entropy (disorder) of the universe. 

Entropy is a thermodynamic quantity that is a measure of disorder or randomness in a system. When a crystalline structure breaks down and a less ordered liquid structure results, entropy increases. For example, the entropy (disorder) increases when ice melts to water. The total entropy of a system and its surroundings always increases for a spontaneous process. The standard entropies, S° are entropy values for the standard states of substances. 

We have seen that while many spontaneous processes, e.g., combustion of organic compounds, are accompanied by liberation of heat (negative AH), others are accompanied by absorption of heat from the surroundings (positive AH). An example of the latter is the melting of ice at a temperature just above 0°C, during which there is a large increase in the entropy of the water. As we have seen, at 0°C at equilibrium T AS is just equal to -AH (Eq. 6-7). 

The First Law of Thermodynamics Any Change in the Energy of a System Requires an Equal and Opposite Change in the Surroundings The Second Law of Thermodynamics In Any Spontaneous Process the Total Entropy of the System and the Surroundings Increases Free Energy Provides the Most Useful Criterion for Spontaneity... 

The Second Law of Thermodynamics In Any Spontaneous Process the Total Entropy of the System and the Surroundings Increases... 

A third statement of the second law is based on the entropy. In reversible systems all forces must be opposed by equal and opposite forces. Consequently, in an isolated system any change of state by reversible processes must take place under equilibrium conditions. Changes of state that occur in an isolated system by irreversible processes must of necessity be spontaneous or natural processes. For all such processes in an isolated system, the entropy increases. Clausius expressed the second law as The entropy of the universe is always increasing to a maximum. Planck has given a more general statement of the second law Every physical and chemical process in nature takes place in such a way as to increase the sum of the entropies of all bodies taking any part in the process. In the limit, i.e., for reversible processes, the sum of the entropies remains unchanged. 

G decreases for a spontaneous process, like the energy of a mechanical system. Since AG incorporates both driving forces for spontaneity—enthalpy (energy) decrease and entropy (disorder) increase—an endothermic process may be spontaneous if the increase in disorder is big enough to counteract the unfavorable enthalpy change, and a process that leads to increased order (negative AS) may be spontaneous if the process is sufficiently exothermic (negative AH). 

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