Thermodynamic systems isolated

Figure 3.1 Schematic representations of thermodynamic systems a) isolated system, b) closed system and c) open 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... 

Thermodynamic systems are parts of the real world isolated for thermodynamic study. The parts of the real world which are to be isolated here are either natural water systems or certain regions within these systems, depending upon the physical and chemical complexity of the actual situation. The primary objects of classical thermodynamics are two particular kinds of isolated systems adiabatic systems, which cannot exchange either matter or thermal energy with their environment, and closed systems, which cannot exchange matter with their environment. (The closed system may, of course, consist of internal phases which are each open with respect to the transport of matter inside the closed system.) Of these, the closed system, under isothermal and iso-baric conditions, is the one particularly applicable for constructing equilibrium models of actual natural water systems. 

A thermodynamic system (closed system) is one that interacts with the surroundings by exchanging heat and work thru its boundary an isolated system is one that does not interact with the surroundings. The state of a system is determined by the values of its various properties, eg, pressure, volume, internal energy, etc. A system can be composed of a finite number of homogeneous parts, called phases, or there can be a single phase. For some applications, it may... 

Isolated Systems Isolated systems exchange neither energy nor matter with the environment. The simplest example from chemical or biological engineering is the adiabatic batch reactor. Isolated systems naturally tend towards their thermodynamic equilibrium with time. This state is characterized by maximal entropy, or the highest possible degree of disorder. 

Equilibrium is a very important concept in discussions of thermodynamics. An isolated system is at equilibrium when it has no tendency to change—a condition that is called internal equilibrium. This implies that the system is at mechanical equilibrium (i.e., it has no tendency for bulk movement of material), thermal equilibrium [i.e., it has no tendency for transport of energy (without bulk movement of material)], and material equilibrium [i.e., it has no tendency for material to change form (such as by a phase transformation or a chemical reaction)]. 

In physics and chemistry we call an ensemble of substances a thermodynamic system consisting of atomic and molecular particles. The system is separated from the surroundings by a boundary interface. The system is called isolated when no transfer is allowed to occur of substances, heat, and work across the boundary interface of the system as shown in Fig. 1.1. The system is called closed when it allows both heat and work to transfer across the interface but is impermeable to substances. The system is called open if it is completely permeable to substances, heat, and work. The open system is the most general and it can be regarded as a part of a closed or isolated system. For instance, the universe is an isolated system, the earth is regarded as a closed system, and a creature such as a human being corresponds to an open system. 

In an irreversible process, in conformity with the second law of thermodynamics, the magnitude that determines the time dependence of an isolated thermodynamic system is the entropy, S [23-26], Consequently, in a closed system, processes that merely lead to an increase in entropy are feasible. The necessary and sufficient condition for a stable state, in an isolated system, is that the entropy has attained its maximum value [26], Therefore, the most probable state is that in which the entropy is maximum. 

Thermodynamic principles arise from a statistical treatment of matter by studying different idealized ensembles of particles that represent different thermodynamic systems. The first ensemble that we study is that of an isolated system a collection of N particles confined to a volume V, with total internal energy E. A system of this sort is referred to as an NVE system or ensemble, as N, V, and E are the three thermodynamic variables that are held constant. N, V, and E are extensive variables. That is, their values are proportional to the size of the system. If we combine NVE subsystems into a larger system, then the total N, V, and E are computed as the sums of N, V, and E of the subsystems. Temperature, pressure, and chemical potential are intensive variables, for which values do not depend on the size of the system. 

This equation matches the classical formulation of the Second Law of thermodynamics for isolated systems. 

In the preceding sections we have derived the thermodynamic conditions for the equilibrium of a system under several different types of constraint. The method of attack has been the same in every case, i.e. to suppose the system isolated by combination with such other systems (thermostats, pressure regulators) as may be necessary to enable it to comply with the conditions of constraint. The second law then tells... 

Second Law The total entropy (disorder) of any isolated thermodynamic system tends to increase over time, approaching a maximum value. This law indicates that disorder increases with every reaction and some energy is always lost to the increase in that disorder. As a result of this law. it is also true that energy transfer always occurs in one direction (heat can pass spontaneously only from a colder to a hotter body). 

In Chapter 4 we established that the entropy function provides a means of mathematically identifying the state of equilibrium in a closed, isolated system (i.e., a system in which M, U, and V are constant). The aim in this section is to develop a means of identifying the equilibrium state for closed thermodynamic systems subject to other constraints, especially those of constant temperature and volume, and constant temperature and pressure. This will be done by first reconsidering the equilibrium analysis for the closed, isolated system used in Sec. 4.1, and then extending this analysis to the study of more general systems. 

For convenience, the thermodynamic systems are assumed closed, isolated from the surroundings. The laws that govern such systems are written in terms of two types of variables the intensive... 

We discuss once more the statements of Clausius. The energy of the world is constant. The entropy of the world tends to a maximum. We reformulate now the term world. For a laboratory experiment we think that can simulate a small world, which is a completely isolated thermodynamic system. We do not know what is at the border of the world however, for our laboratory world we think there are no constraints at the border. This idea corresponds to a real world that should be embedded in an empty space. 

We imagine an example for the thermodynamic system under consideration Assume, the system is a gas in a cylinder with freely movable piston. The cylinder is isolated thermally. The environment is the atmosphere. Then the gas may be in equilibrium with respect to compression energy, because it can change freely the volume Vsys. Therefore, the pressure of the system psys is equal to the atmospheric pressure ... 

Closed Systems Thermodynamic systems in which only energy may be exchanged with the surroundings. The system is closed, containing constant mass, but is not isolated. 

Adiabatic (thermally) Isolated Systems Thermodynamic systems in which no heat or mass transfer with the surroundings takes place, although exchange of energy in other forms, e.g., shaft work, is possible. 

Closed (isolated) Systems Thermodynamic systems in which no exchange of energy or matter occurs with the surroundings. 

For convenience, thermodynamic systems are usually assumed closed, isolated from the surroundings. The laws that govern such systems are written in terms of two types of variables intensive (or intrinsic) that do not depend on the mass and extensive that do. By definition, extensive variables are additive, that is, their value for the whole system is the sum of their values for the individual parts. For example, volume, entropy, and total energy of a system are extensive variables, but the specific volume (or its reciprocity - the density), molar volume, or molar free energy of mixing are intensive. It is advisable to use, whenever possible, intensive variables. 

It is one of the paradoxes of thermodynamics that isolated systems, that have no counterpart in the real world, are possibly the most important of all in terms of our understanding of chemical reactions. You will have to wait until Chapter 4 to see why. 

In mechanics, the state of rest is called state of static equilibrium and Equation E3.4 is viewed as the law of equilibrium. Actually, it is rather an equation of conservation than a law or an autonomous principle This equation merely results from hypotheses made on the system (isolation and indeformability) and from the application of the First Principle of Thermodynamics (Equation E3.2). In the Formal Graph theory, this classical notion of static equilibrium, expressed by a zero sum of forces or of torques, is considered as unsuitable because it cannot be generalized outside mechanics (see remark on Notion hard to generalize ). 

A thermodynamic system is separated from the remainder of the universe by a boundary and everything outside this boundary is known as the surrounding. Exchanges of work, heat, or matter between the system and the surroundings take place across this boundary. The systems are categorized as open, closed and isolated depending on the types of interactions involved. 

For an open (or isolated) system (exchange neither energy nor matter with their surrounding), the entropy or AG changes monotonically in a spontaneous method. A scheme for two basic thermodynamic systems is presented in Fig. 1.1... 

Such an attitude to equilibrium thermodynamics - the science which revealed irreversibility of the evolution of isolated systems and asymmetry of natural processes with respect to time - is related to some circumstances that require a thorough analysis. Here we will emphasize only one of them which is the most important for imderstanding further text. It lies in the fact that the most important notion of thermodynamics, i.e. equilibrium, became interpreted exclusively as the state of rest (absence of any forces and flows in the thermodynamic system) and equilibrium processes - as those identical to reversible ones. These one-sided interpretations ignored the Galileo principle of relativity, the third law of Newton and the Boltzmann probabilistic interpretations of entropy that allow dynamic interpretations of equilibria and irreversible interpretations of equilibrium processes. 

Straining a body involves forces and displacements. Therefore, work is done in this process. To calculate this work we consider the body as a thermodynamic system that is closed but not isolated. All matter and points not belonging to the body under consideration constitute the surroundings of this system. By designating the system to be closed we infer that the boundary between the system and its surroundings does not allow any mass transfer. For an isolated system the boundary would in addition exclude the transfer of all energy. 

A statistical ensemble is a (mental or virtual) collection of a very large number of systems, each constructed to be a replica on a thermodynamic (macroscopic) level of the real thermodynamic system of interest. Among the usual ensemble, the isolated microcanonical ensemble with fixed N,V,E is useful for theoretical discussion. For more practical applications, however, non-isolated systems are considered, like the canonical ensemble in which N, V and T fixed (Me Quarrie, 1977, p. 37). Other standard ensembles exist such as the Gibbs ensemble employed here destined to phase equilibrium calculations and described afterwards. 

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