Thermodynamic state of system

State precisely the meaning of each of the following terms. Y)u may need to review Chapter 1 to refresh your memory about terms introduced there, (a) heat (b) temperature (c) system (d) surroundings (e) thermodynamic state of system (f) work. 

Thermodynamic states of systems near a critical point are characterized by the presence of large fluctuations of the order parameter associated with the critical phase transition. For one-component fluids near the vapor-liquid critical point the order parameter can be identified with the fluctuating density p. That is, near the vi r-liquid critical point the local density becomes a function of the position r. The density fluctuations have a pronounced effect on the behavior of both the thermodynamic and the transport properties of fluids in the critical region. Specifically, they lead to a strong enhancement of the thermal conductivity and to a weak enhancement of the viscosity of fluids in the critical region, as will be elucidated in this chapter. 

Like the engine-based statements, Caratheodory s statement invokes limitations. From a given thermodynamic state of the system, there are states that cannot be reached from the initial state by way of any adiabatic process. We will show that this statement is consistent with the Kelvin-Planck statement of the Second Law. 

A surface is that part of an object which is in direct contact with its environment and hence, is most affected by it. The surface properties of solid organic polymers have a strong impact on many, if not most, of their apphcations. The properties and structure of these surfaces are, therefore, of utmost importance. The chemical stmcture and thermodynamic state of polymer surfaces are important factors that determine many of their practical characteristics. Examples of properties affected by polymer surface stmcture include adhesion, wettability, friction, coatability, permeability, dyeabil-ity, gloss, corrosion, surface electrostatic charging, cellular recognition, and biocompatibility. Interfacial characteristics of polymer systems control the domain size and the stability of polymer-polymer dispersions, adhesive strength of laminates and composites, cohesive strength of polymer blends, mechanical properties of adhesive joints, etc. 

In summary, it is clear that water absorbs into amorphous polymers to a significant extent. Interaction of water molecules with available sorption sites likely occurs via hydrogen bonding such that the mobility of the sorbed water is reduced and the thermodynamic state of this water is significantly altered relative to bulk water. Yet accessibility of the water to all potential sorption sites appears to be dependent on the previous history and physical-chemical properties of the solid. In this regard, the water-solid interaction in amorphous polymer systems is a dynamic relationship depending quite strongly on water activity and temperature. 

An emulsion is a dispersed system of two immiscible phases. Emulsions are present in several food systems. In general, the disperse phase in an emulsion is normally in globules 0.1-10 microns in diameter. Emulsions are commonly classed as either oil in water (O/W) or water in oil (W/O). In sugar confectionery, O/W emulsions are most usually encountered, or perhaps more accurately, oil in sugar syrup. One of the most important properties of an emulsion is its stability, normally referred to as its emulsion stability. Emulsions normally break by one of three processes creaming (or sedimentation), flocculation or droplet coalescence. Creaming and sedimentation originate in density differences between the two phases. Emulsions often break by a mixture of the processes. The time it takes for an emulsion to break can vary from seconds to years. Emulsions are not normally inherently stable since they are not a thermodynamic state of matter. A stable emulsion normally needs some material to make the emulsion stable. Food law complicates this issue since various substances are listed as emulsifiers and stabilisers. Unfortunately, some natural substances that are extremely effective as emulsifiers in practice are not emulsifiers in law. An examination of those materials that do stabilise emulsions allows them to be classified as follows ... 

The stable equilibrium thermodynamic state of a system at constant pressure and temperature is the one with the minimum Gibbs free energy, G. This thermodynamic condition is defined as ... 

The basic equations used to predict the thermodynamic properties of systems for the SRK and PFGC-MES are given in Tables I and II, respectively. As can be seen, the PFGC-MES equation of state relies only on group contributions--critical properties etc., are not required. Conversely, the SRK, as all Redlich-Kwong based equations of states, relies on using the critical properties to estimate the parameters required for solution. 

Gibbs phase rule phys chem A relationship used to determine the number of state variables F, usually chosen from among temperature, pressure, and species composition in each phase, which must be specified to fix the thermodynamic state of a system in equilibrium F = C - P - M+2, where C is the number of chemical species presented at equilibrium, P is the number of phases, and M is the number of independent chemical reactions. Also known as Gibbs rule phase rule. gibz faz, rijl I... 

A psychologist develops a theory that states of mind (anger, suspicion, greed) are thermodynamic states of a region of the brain that can be considered a system... 

In the field of food colloids, the use of molecular thermodynamics provides a set of qualitative and quantitative relationships describing fundamental phenomena occurring in the equilibrium state of systems for which the intermolecular interactions of biopolymers (proteins and polysaccharides) play a key role. The phenomena and processes amenable to discussion from the thermodynamic point of view are ... 

Monte Carlo simulations are performed within a statistical ensemble. In the canonical ensemble (with the number of molecules, volume, and temperature fixed), the average value of a thermodynamic quantity, (T(x)), as a function of the states of system, x, is given by... 

The basic equations governing elementary chemical kinetics were introduced and discussed in Chapter 9. However, the discussion there is primarily concerned with how the molar production of chemical species (i.e., wk) depends on elementary reactions, which in turn depend on the species composition and the thermodynamic state of the gases. The objective here is to impose further constraints on the system to describe certain physical situations. Specifically, we consider the imposition of various combinations of fixed temperature, volume, and pressure. 

We have previously emphasized (Section 2.10) the importance of considering only intensive properties Rt (rather than size-dependent extensive properties Xt) as the proper state descriptors of a thermodynamic system. In the present discussion of heterogeneous systems, this issue reappears in terms of the size dependence (if any) of individual phases on the overall state description. As stated in the caveat regarding the definition (7.7c), the formal thermodynamic state of the heterogeneous system is wholly / dependent of the quantity or size of each phase (so long as at least some nonvanishing quantity of each phase is present), so that the formal state descriptors of the multiphase system again consist of intensive properties only. We wish to see why this is so. 

With an open system to which electrodes are attached, we can study the stability of interface morphology in an external electric field. A particularly simple case is met if the crystals involved are chemically homogeneous. In this case, Vfij = 0, and the ions are essentially driven by the electric field. Also, this is easy to handle experimentally. The counterpart of our basic stability experiment (Fig. 11-7) in which the AO crystal was exposed to an oxygen chemical potential gradient is now the exposure of AX to an electric field from the attached electrodes. In order to define the thermodynamic state of AX, it is necessary to apply electrodes with a predetermined... 

The phase rule offers a simple means of determining the minimum number of intensive variables that have to be specified in order to unambiguously determine the thermodynamic state of the system. 

Note that y phase does not exist as a stable phase at the present temperature and pressure. In other words, if y phase is seen in the structure, then the system is not in die equilibrium, but a meta-stable, non-equilibrium state. However, if the thermodynamic state of the system is changed (e.g., different temperature or pressure), y phase may exist as a stable phase in a certain composition range ... 

The thermodynamic state of a polymer- solvent system is completely determined, as it was analized before, at fixed temperature and pressure by means of the interaction parameter g. This g is defined through the noncombinatorial part of the Gibbs mixing function, AGm- The more usual interaction parameter, x, is defined similarly but through the solvent chemical potential, A xi, derived from AGm-... 

Rates of reactions are functions of the thermodynamic state of the system. For a simple system, fixing temperature and composition fixes the rest of the thermodynamic quantities or the state. Thus, the rate can be written in terms of a temperature-dependent term called the rate constant k (constant at fixed temperature) and a concentration term or terms C). a. Example... 

It is possible to define the thermodynamic state of a system in terms of groups of certain independent variables, and T, X, x, D and E are available in the present case. For example, the equilibrium could be expressed in terms of the... 

Antsiferov, E. G., Kaganovich, B. M., Semeney, P. T. and Takayshwily, M. K., "Search for the Intermediate Thermodynamic States of Physicochemical Systems. Numerical Methods of Analysis and their Applications", pp. 150-170. SEI SO AN SSSR, Irkutsk (1987). (in Russian). 

To discuss the phase stability of polymer blends in more detail one has to specify the free-energy parameter X. This can be done in terms of an equation-of-state theory [8]. Theories that take into account the compressible nature of the pure components as well as that of the mixture are called equation-of-state theories. As basic quantities characterizing the thermodynamic state of a system the reduced temperature (T), volume (V) and pressure (P) are employed and defined by... 

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. 

Again, the term macrostate refers to the thermodynamic state of the composite system, defined by the variables N, E, and V2, E2. A more probable macrostate will be one that corresponds to more possible microstates... 

As indicated in Chapter 2, the adsorbent surface is characterized by a surface tension y whose magnitude depends on the nature of the surrounding medium (liquid, gas or vacuum) with which the adsorbent is in equilibrium. The isothermal extension of the surface area A, with no other change in the thermodynamic state of the system of adsorption, results in an increase d F of the Helmholtz energy of the system. Thus, the surface tension, y, is defined as ... 

Engineering systems mainly involve a single-phase fluid mixture with n components, subject to fluid friction, heat transfer, mass transfer, and a number of / chemical reactions. A local thermodynamic state of the fluid is specified by two intensive parameters, for example, velocity of the fluid and the chemical composition in terms of component mass fractions wr For a unique description of the system, balance equations must be derived for the mass, momentum, energy, and entropy. The balance equations, considered on a per unit volume basis, can be written in terms of the partial time derivative with an observer at rest, and in terms of the substantial derivative with an observer moving along with the fluid. Later, the balance equations are used in the Gibbs relation to determine the rate of entropy production. The balance equations allow us to clearly identify the importance of the local thermodynamic equilibrium postulate in deriving the relationships for entropy production. 

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