Thermodynamics macroscopic topics

The topic of capillarity concerns interfaces that are sufficiently mobile to assume an equilibrium shape. The most common examples are meniscuses, thin films, and drops formed by liquids in air or in another liquid. Since it deals with equilibrium configurations, capillarity occupies a place in the general framework of thermodynamics in the context of the macroscopic and statistical behavior of interfaces rather than the details of their molectdar structure. In this chapter we describe the measurement of surface tension and present some fundamental results. In Chapter III we discuss the thermodynamics of liquid surfaces. 

Frequently, however, the stability and, more generally, the microstructure and the macroscopic states of dispersions are determined by kinetic and thermodynamic considerations. Thermodynamics dictates what the equilibrium state will be, but it is often the kinetics that determines if that equilibrium state will be reached and how fast. This becomes a consideration of special importance in practice since most processing operations involve dynamic variables such as flow, sedimentation, buoyancy, and the like. Although a detailed discussion of this is beyond our scope here, it is important that we consider at least one example so that we can place some of the topics we discuss in this chapter in proper context. 

The topic of interactions between Lewis acids and bases could benefit from systematic ab initio quantum chemical calculations of gas phase (two molecule) studies, for which there is a substantial body of experimental data available for comparison. Similar computations could be carried out in the presence of a dielectric medium. In addition, assemblages of molecules, for example a test acid in the presence of many solvent molecules, could be carried out with semiempirical quantum mechanics using, for example, a commercial package. This type of neutral molecule interaction study could then be enlarged in scope to determine the effects of ion-molecule interactions by way of quantum mechanical computations in a dielectric medium in solutions of low ionic strength. This approach could bring considerable order and a more convincing picture of Lewis acid base theory than the mixed spectroscopic (molecular) parameters in interactive media and the purely macroscopic (thermodynamic and kinetic) parameters in different and varied media or perturbation theory applied to the semiempirical molecular orbital or valence bond approach [11 and references therein]. 

The topic arises from the following sequence of aspects of entropy when entropy is introduced on a thermodynamic basis the issue is the motion of heat (Jaynes, 1988), and the assessment involves calorimetry an entropy change is evaluated. When entropy is formalized with the classical view of statistical thermodynamics, the entropy is found by evaluating a configurational integral (Bennett, 1976). But a macroscopic physical system at a particular thermodynamic state has a particular entropy, a state function, and the whole description of the physical system shouldn t involve more than a mechanical trajectory for the system in a stationary, equilibrium condition. How are these different concepts compatible ... 

Explicitly, we look at some experiments seeking (a) to come fairly directly at the nonmechanical state functions of thermodynamics, such as the entropy and free energy, (b) to obtain information about quantum-mechanical fluids, and (c) to choose boundary conditions so that one obtains information not about the interior of a macroscopic system, but about some microscopic region. These three excursions are made in Sections 2, 3, and 4, respectively. Rather more attention is given to the first of the three topics than the others, since there has been more activity along this line. 

The basic, macroscopic theories of matter are equilibrium thermodynamics, irreversible thermodynamics, and kinetics. Of these, kinetics provides an easy link to the microscopic description via its molecular models. The thermodynamic theories are also connected to a microscopic interpretation through statistical thermodynamics or direct molecular dynamics simulation. Statistical thermodynamics is also outlined in this section when discussing heat capacities, and molecular dynamics simulations are introduced in Sect 1.3.8 and applied to thermal analysis in Sect. 2.1.6. The basics, discussed in this chapter are designed to form the foundation for the later chapters. After the introductory Sect. 2.1, equilibrium thermodynamics is discussed in Sect. 2.2, followed in Sect. 2.3 by a detailed treatment of the most fundamental thermodynamic function, the heat capacity. Section 2.4 contains an introduction into irreversible thermodynamics, and Sect. 2.5 closes this chapter with an initial description of the different phases. The kinetics is closely link to the synthesis of macromolecules, crystal nucleation and growth, as well as melting. These topics are described in the separate Chap. 3. 

In the following chapters thermodynamics is frequently applied to derive relations between macroscopic parameters. In writing this book, it is assumed that the reader is familiar with the basics of thermodynamics of reversible processes. Nevertheless, this chapter is included as a reminder. It presents a concise summary of thermodynamic principles that are relevant in view of the topics discussed in forthcoming chapters, and special attention is paid to heterogeneous systems that contain phase boundaries. 

If we look at a small portion of a macroscopic system or study a mesoscopic system, we must study fluctuations. The probability of fluctuations is phenomenologically described by the thermodynamic theory of fluctuations (5). From the ensemble theory point of view, the fluctuation theory is the study of large deviations from the expectation value. This is the reason why large deviation theory is becoming increasingly important in statistical thermodynamics. Standard works on large deviation theory are References 16 and 17 perhaps as accessible introduction to the topic may be found in Reference 18. 

Reviewed herein are some of the fundamental concepts associated with chemical equilibrium, chemical thermodynamics, chemical kinetics, aqueous solutions, acid-base chemistry, oxidation-reduction reactions and photochemistry, all of which are essential to an understanding of atmospheric chemistry. The approach is primarily from the macroscopic viewpoint, which provides the tools needed by the pragmatist. A deeper understanding requires extensive treatment of ihe electronic structure of matter and chemical bonding, topics that are beyond the scope of this introductory text. This book can be used for either self-instruction, or as the basis for a short introductory class... 

In this chapter we shall be concerned with the basic principles that govern the crystallization behavior of flexible long-chain molecules. The more-rigid type of polymers will be discussed in Chapter 5. The subject matter divides itself naturally into several interrelated subdivisions. These include thermodynamics of crystallization, kinetics and mechanisms of crystallization, structure and morphology, and microscopic and macroscopic properties. We shall discuss each of these topics in terms of fundamental physical and chemical concepts. There is an interrelation among the various aspects of polymer crystallization as is indicated by the chart given in Fig. 4.1. 

In chemistry, the study of large, or macroscopic, systems involves thermodynamics in small, or microscopic, systems, it can involve quantum mechanics. In systems that change their structures over time, the topic is kinetics. But they all have basic connections with thermodynamics. We will begin the study of physical chemistry with thermodynamics the study of heat and work in chemistry. 

The study of macroscopic properties involves thermodynamics, which is the major topic of this volume, along with gas kinetic theory, transport processes, and reaction kinetics. Quantum mechanics, spectroscopy, and statistical mechanics are molecular topics and are discussed in Parts 3 and 4 of this textbook. 

Since the basic ideas in surfactant science have been introduced, one can now proceed with the main topic of this chapter macroemulsion stability. Macroemulsions are formed by mechanical mixing of oil and water in the presence of surfactants, e.g. by mixing the phases of the Winsor 1 equilibrium in each other. As a result of mixing, one of the phases breaks into macroscopic droplets, while the other stays continuous. Macroemulsions are thermodynamically unstable and gradually resolve with time into two distinct layers. However, in some cases they show a remarkable kinetic stability. Most experimental trends in macroemulsion stability were established a long time ago and will be outlined below. 

Under Kurt Uberreiter further research was carried out on the thermodynamic properties of polymers and their solutions. In addition, Uberreiter oversaw research into topics such as crystallization delaying and accelerating structural elements and the relationship between molecular structure and macroscopic properties. This included the first measurement in polymer solutions of effects from configuration on surface tension. Members of the department aiso built a wide array of instruments, such as high pressure dilatometers, differential refractometers... 

---