Isolated system, definition

The slopes of the fimctions shown provide the reaction rates according to the various definitions under the reaction conditions specified in the figure caption. These slopes are similar, but not identical (nor exactly proportional), in this simple case. In more complex cases, such as oscillatory reactions (chapter A3.14 and chapter C3.6). the simple definition of an overall rate law tluough equation (A3.4.6) loses its usefiilness, whereas equation (A3.4.1) could still be used for an isolated system. 

A term used in thermodynamics to designate a region separated from the rest of the universe by definite boundaries. The system is considered to be isolated if any change in the surroundings the portion of the universe outside of the boundaries of the system) does not cause any changes within the system. See Closed System Isolated System Open System... 

In addition to the general concept of a system, we define different types of systems. An isolated system is one that is surrounded by an envelope of such nature that no interaction whatsoever can take place between the system and the surroundings. The system is completely isolated from the surroundings. A closed system is one in which no matter is allowed to transfer across the boundary that is, no matter can enter or leave the system. In contrast to a closed system we have an open system, in which matter can be transferred across the boundary, so that the mass of a system may be varied. (Flow systems are also open systems, but are excluded in this definition because only equilibrium systems are considered in this book.)... 

Similarly, if one is interested in a macroscopic thermodynamic state (i.e., a subset of microstates that corresponds to a macroscopically observable system with bxed mass, volume, and energy), then the corresponding entropy for the thermodynamic state is computed from the number of microstates compatible with the particular macrostate. All of the basic formulae of macroscopic thermodynamics can be obtained from Boltzmann s definition of entropy and a few basic postulates regarding the statistical behavior of ensembles of large numbers of particles. Most notably for our purposes, it is postulated that the probability of a thermodynamic state of a closed isolated system is proportional to 2, the number of associated microstates. As a consequence, closed isolated systems move naturally from thermodynamic states of lower 2 to higher 2. In fact for systems composed of many particles, the likelihood of 2 ever decreasing with time is vanishingly small and the second law of thermodynamics is immediately apparent. 

As far as I am aware, independent experimental evidence for the values of the surface potential and salt fractionation factor have not been obtained for any system other than the n-butylammonium vermiculite gels. For this isolated system, the predicted values of 5 from the Donnan equilibrium and the new equilibrium based on the coulombic attraction theory, namely 4.0 and 2.8, respectively, are definitely distinguished by the experimental results. It would be highly desirable to obtain further tests of our prediction for 5 in systems of interacting plate macroions, both in clay science and lamellar surfactant phases. 

An isolated system has a definite amount of energy and matter and it cannot exchange them with the surroundings. 

In the last chapter we showed that an isolated system is in equilibrium when its entropy is a maximum. In chemistry and physics, however, most of the systems with which we have to deal are not isolated, and it is therefore a question of importance to determine under what circumstances a system will be in equihbrium when its interaction with the surroundings is prescribed in some definite manner. 

As we have seen, both models considered in the previous pages lead to the definition of a microscopic portion of the whole liquid system, the larger portion of the liquid being treated differently. We may rationalize this point by introducing, in the quantum mechanical language, an effective Hamiltonian of the subsystem (A B-Sn), where the Hamiltonian of the isolated system M = A-B Ch°M) is supplemented by an effective solute-solvent interaction potential (Vint)-... 

By definition, the microcanonical ensemble contains all possible configurations in the 6N-dimensionaI phase space with the same energy and a constant probability of being in each configuration N is the number of particles in the system under consideration. This ensemble describes an isolated system with constant N and V, or constant N and zero external pressure [28]. Constant-energy simulations are not recommended for equilibration because, without the energy flow facilitated by the temperature control methods, the desired temperature cannot be achieved. However, during the data collection phase, if one is... 

Schweitz was the first to recognize that the definition of pressure is a problem in the physics of an open system. He argued that the classical result based on the properties of a closed, isolated system - a petit ensemble - must be recast in terms of an open system, a system with permeable walls, replacing the petit ensemble with the grand ensemble. This he did for both a classical... 

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. 

The definition of vibrational intensities for molecules in solution requires some modifications with respect to the isolated system. The presence of the solvent in fact modifies not only the solute charge distribution but also the probing electric field acting on the molecule. As we shall see in the following sections, this is a problem of general occurrence when an external field interacts with a molecule in a condensed phase (historically it is known as local field effect ). 

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