Spontaneity natural processes

Position C does not correspond to the lowest minimum of the energy following a small displacement, the block will return to the initial position whereas large displacements will move the block to the more stable position A. In A there is an (absolutely) stable equilibrium and in C a metastable equilibrium. For this mechanical system the stability conditions and the trends of spontaneous (natural) processes are related to minima (relative or absolute) of the gravitational potential energy. 

The following consideration of Planck (8 Vorlesungen uber theoretische PhysiJc, 1910, p. 16) will facilitate the conception of entropy, and thus help us to understand the second law. Let a spontaneous natural process in an isolated system lead... 

Today, scientists have an extensive array of analytical methods at their disposal photometry, HPLC, GC analysis and MS online. Samples of submersion cultures are made available with the aid of a tapping and preparation unit. Complete R D programmes can be run automatically nowadays and automation will foreseeably take over production processes. Historically, automation has strong roots in Switzerland, as is shown by the contribution by W. Beyeler et al. [16] in this issue. With the current period of automation, a century comes to a close that - once it had overcome the myth of spontaneous creation - has tried to establish control over spontaneous natural processes by simple means. 

Thus, the first law of thermodynamics is the manifestation of the principle of conservation of energy in the form of heat and mechanical work. It states that heat transfer is equivalent to work done, but does not specify the direction of heat transfer and work done. The limitation of the first law was that it did not specifically give the direction of spontaneous natural processes. This limitation was overcome by the second law of thermodynamics. 

Passive systems Solar-thermal systems in which heat transfer takes place predominantly by spontaneous (natural) processes, if CoP > 50. 

Yet this observation of the one-way character of spontaneous natural processes is so universal that it is one of the most basic observations of nature. It has been given a name, the second law of thermodynamics, although, historically, it partially precedes the first. Those most important in formulating it were Carnot, Clausius, and Kelvin [2]. Like the first law, Newton s laws, or the law of conservation of matter, it cannot be derived from any more basic law rather, it rests on its ability to explain all the observations ever made to test it. This law appears in many forms and has very far-reaching consequences. Many scientists believe that the second law is the most fundamental of all the laws of nature. 

The process described above is usually called osmosis and this usually imphes a flow of fluid in one direction or the other. If the permeating species, usually called the solvent, flows from the pure compartment to the mixture compartment then it is called osmosis pure and simple. This seems the natural process since the solvent dilutes the solution and this involves an increase in entropy and/or a decrease in free energy, so the resultant flow is spontaneous and the system tends to equihbrium. However, the starting conditions may be such that the difference of pressure... 

In equation (2.40), the equality applies to the reversible process and the inequality to the spontaneous or natural process. 

Once the spontaneous direction of a natural process is determined, we may wish to know how far the process will proceed before reaching equilibrium. For example, we might want to find the maximum yield of an industrial process, the equilibrium solubility of atmospheric carbon dioxide in natural waters, or the equilibrium concentration of a group of metabolites in a cell. Thermodynamic methods provide the mathematical relations required to estimate such quantities. 

For a scientist, the primary interest in thermodynamics is in predicting the spontaneous direction of natural processes, chemical or physical, in which by spontaneous we mean those changes that occur irreversibly in the absence of restraining forces—for example, the free expansion of a gas or the vaporization of a hquid above its boiling point. The first law of thermodynamics, which is useful in keeping account of heat and energy balances, makes no distinction between reversible and irreversible processes and makes no statement about the natural direction of a chemical or physical transformation. 

A simple statement of the Second Law is natural processes are accompanied by an increase in the entropy of the universe. There are several other statements of the Second Law in the chapter Notes. As noted above, entropy is a measure of disorder the greater the extent of disorder, the greater the entropy. The Second Law tells us that things change spontaneously in a way that increases disorder. At equilibrium, entropy is maximized and disorder reigns. 

The second law of thermodynamics, as formulated by Kelvin, states that no process is possible in which the sole result is the absorption of heat from a reservoir and its complete conversion into work in other words, in any natural process involving a transfer of energy, some energy is converted irreversibly into heat that cannot be involved in further exchange. The second law of thermodynamics, therefore, is a recognition of spontaneous and nonspontaneous processes and the fact that natural processes have a sense of direction. 

Integration of FETs into circuitry is one of the ultimate technology demonstrations, requiring many devices to be fabricated with near-uniform electrical characteristics. For the SAMFETs, the spontaneous nature of the assembly process renders it particularly attractive for low-cost, large-area electronics. The micron-scale channel a-substituted quinquethiophene SAMFETs were quickly implemented in different electronic circuits, with FETs having Si02 and SU8 gate dielectrics [70, 72]. 

In Chapter 1 we mentioned Oparin s bold idea that the transition to life was based upon a gradual and spontaneous increase of molecular complexity. This ordering process in a prebiotic scenario must have taken place without the intelligence of enzymes and without the memory of nucleic acids, as by dehnition these did not yet exist. At first sight, this whole idea appears then to be at odds with the second law of thermodynamics and the common belief that natural processes preferentially bring about an increase of entropy/disorder. 

The natural radiative lifetime is independent of temperature, but is susceptible to environmental perturbations. Under environmental perturbation, such as collisions with the solvent molecules or any other molecules present in the system, the system may lose its electronic excitation energy by nonradiative processes. Any process which tends to compete with spontaneous emission process reduces the life of an excited state. In an actual system the average lifetime t is less than the natural radiative lifetime as obtained from integrated absorption intensity. In many polyatomic molecules, nonradiative intramolecular dissipation of energy may occur even in the absence of any outside perturbation, lowering the inherent lifetime. 

For a certain set of chemical species concentrations, temperature, and pressure, a chemical process will proceed in the direction that decreases the free energy. If AG < 0 for that set of concentrations, and so forth, the process will proceed spontaneously in the direction of the forward reaction, although thermodynamics says nothing about the rate at which it will proceed. If AG > 0, the reaction will proceed in the reverse direction spontaneously. The process proceeds in the direction to minimize the free energy of the system until AG = 0, at which point equilibrium has been attained. Stated another way, natural processes always proceed in the direction that decreases the free energy, until equilibrium is reached. 

These three examples (and many others that might be imagined) indicate that the first law is inadequate to provide a complete picture of the intrinsic natural time-ordering or directionality of spontaneous thermal processes. As discussed in Section 3.2 (see Table 3.1), the irreversibility of spontaneous natural events ( time s arrow ) is deeply tied to dissipative heating effects that underlie thermodynamic theory. Proper characterization of spontaneity and irreversibility in thermal processes therefore requires a further extension of the inductive basis of thermodynamic theory the second law of thermodynamics. 

A thermodynamic process is said to have taken place if a change is observed to have taken place in any macroscopic property of the system. An infinitesimal process is a process in which there is only an infinitesimal change in any macroscopic property of the system. A natural process is an infinitesimal process that occurs spontaneously in real systems an unnatural process is one that cannot occur spontaneously in real systems. Reversible processes are either natural or unnatural processes which can occur in either direction between two states of equilibrium... 

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. 

A process, which involves the spontaneous change of a system from a state to some other state, is called spontaneous or natural process. As such a process cannot be reversed without help of an external agency, the process is called an irreversible process. 

Entropy increases in all irreversible, spontaneous or natural processes. 

The essential realization in this spontaneous ordering process is the importance of noncovalent bonding interaction between molecules, that is, supramolecular chemistry. These conformation-specific interactions are governed by weak forces including hydrogen bonding, metal coordination, van der Waals forces, pi-pi interactions, and electrostatic Coulombic effects. The cooperative action of multiple noncovalent interaction forces is precisely the path nature takes to produce shape and form. 

From the discussion of heat engines, the second law of thermodynamics states that it is impossible to achieve heat, taken from a reservoir, and convert it into work without simultaneous delivery of heat from the higher temperature to the lower temperature (Lord Kelvin). It also states that some work should be converted to heat in order to make heat flow from a lower to a higher temperature (Principle of Clausius). These statements acknowledge that the efficiency of heat engines could never be 100% and that heat flow from high temperatures to low temperatures is not totally spontaneous. Simply, the second law states that natural processes occur spontaneously toward the direction in which less available work can be used. 

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