Spontaneous process thermodynamic conditions

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... 

The above form of the thermodynamic representation of the condition for the occurrence of a spontaneous process or of equilibrium is frequently used. 

Thermodynamics is the branch of science dealing with the energetics of substances and processes. It describes the tendency of processes to take place spontaneously, the effects of external conditions, and the effects of the composition of mixtures on such processes. Thermodynamics is generally capable of correlat-... 

The first steps towards molecular complexity must have been based on spontaneous reactions - reactions that occurred because they were under thermodynamic control. As we have learned in Chapter 1, this does not mean that there is a causal chain of thermodynamic events leading to life, since a given thermodynamic output depends on the initial conditions (as is always the case in thermodynamics) these are often determined by the laws of contingency - the given temperature or pressure or concentration for that particular process. Thermodynamic control means, however, that if the same reaction is repeated under the same initial conditions, the same results are obtained - as exemplified by Miller s reaction in the famous flask under simulated reducing atmospheric conditions. 

Inequalities (3.2) and (3.3) are generalizations of the principle of the minimal entropy production rate in the course of spontaneous evolution of its system to the stationary state. They are independent of any assump tions on the nature of interrelations of fluxes and forces under the condi tions of the local equilibrium. Expression (3.2), due to its very general nature, is referred to as the Qlansdorf-Prigogine universal criterion of evolution. The criterion implies that in any nonequilibrium system with the fixed boundary conditions, the spontaneous processes lead to a decrease in the rate of changes of the entropy production rate induced by spontaneous variations in thermodynamic forces due to processes inside the system (i.e., due to the changes in internal variables). The equals sign in expres sion (3.2) refers to the stationary state. 

A thermodynamic quantity that is a measure of the disorder or randomness in a system. For example, a crystal structure changing to a liquid is associated with an increase in entropy as, for example, the melting of ice crystals forming water under standard conditions. Entropy increases for a spontaneous process. S refers to entropy values in standard states of substances. 

In thermodynamics (see e.g. [1]) it is shown that for any isolated (closed) system (which does not exchange energy with its surroundings), spontaneous transformations take place with an increase in the entropy AS of the system. For a non-isolated system in isothermal conditions, spontaneous processes take place with a negative variation of free enthalpy AG where... 

In preparation for setting up the second law of thermodynamics and stating precisely the criteria for spontaneity, we will examine several familiar examples of spontaneous processes and describe their features in general terms. A spontaneous change is one that can occur by itself without outside intervention, once conditions have been established for its initiation. The change may be fast or slow, and we may have to wait a significant period to determine whether it does occur. 

This means that in a state of thermodynamic equilibrium at constant temperor ture and volume, the work function is a minimum under the same conditions a spontaneous process is accompanied by a decrease in the work function. 

I believe that empirical observations only attain the status of laws when they are accompanied by theories that support their generality or, sometimes, show their limitations. The second law of thermodynamics, with which I began this chapter, is surely a case in point. The claim that spontaneous processes will always increase the entropy of the universe is something that one can accept as a law primarily because of the statistical argument that there are more ways for things to be disordered than ordered. Certainly, one wants experimental studies to bolster the claim, but such studies by themselves would not be convincing because of the general inductive problem of empirical science—one could never rule out the possibility that some particular set(s) of conditions not studied in the experimental tests would lead to an exception to the... 

For constant temperature and pressure, dG = 0 defines the condition of an equilibrium state. The second law of thermodynamics requires for spontaneous processes that... 

The synthesis of glucose directly from CO2 and H2O and the synthesis of proteins directly from amino acids are both non-spontaneous processes under standard conditions. Yet it is necessary for these to occur for life to exist. In light of the second law of thermodynamics, how can life exist ... 

Because of this, always, at any irreversible spontaneous process, due to heat dissipation, dS > 0. In conditions of a reversible process, i.e., stable thermodynamic equilibrium, heat does not dissipate, and entropy value does not change. Such processes, at which dS = 0, are called adiabatic. Overall, for all spontaneous processes is valid inequation... 

SO that A always decreases in spontaneous processes under constant T, V conditions. It is another thermodynamic potential. 

---