Macroscopic realm

It should be noted that this property of energy becoming less useful as we use it is purely a characteristic of the macroscopic realm. In the microscopic world, energy is continually transformed between kinetic and potential forms, as in a vibrating molecule, or between molecular energy and radiation, as in a molecule in a laser cavity. How microscopic systems combine to give the very different energy properties of macroscopic systems will be the subject material of Chapter 5. 

Colloids are systems with size intermediate between the microscopic and macroscopic realms. They have been defined as particles with a characteristic dimension between a micron and a few nanometers or, alternatively, as entities containing between 103 and 109 atoms. With their small size, colloids have a very large surface-to-volume ratio and surface interactions are dominant in determining their stability. Some properties of systems in the colloidal size range are as follows ... 

Electrons residing in molecular clusters can be viewed as microscopic probes of both the local liquid structure and the molecular dynamics of liquids, and as such their transitory existence becomes a theoretical and experimental metaphor for one of the major fundamental and contemporary problems in chemical and molecular physics, that is, how to describe the transition between the microscopic and macroscopic realms of physical laws in the condensed phase. Since this chapter was completed in the Spring of 1979, several new and important observations have been made on the dynamics and structure of e, which, as a fundamental particle interacting with atoms and molecules in a fundamental way, serves to assist that transformation for electronic states in disordered systems. In a sense, disorder has become order on the subpicosecond time-scale, as we study events whose time duration is shorter than, or comparable to, the period during which the atoms or molecules retain some memory of the initial quantum state, or of the velocity or phase space correlations of the microscopic system. This approach anticipated the new wave of theoretical and experimental interest in developing microscopic theories of... 

Every change in the observable world—from boiling water to the changes that occur as our bodies combat invading viruses—has its basis in the world of atoms and molecules. Thus, as we proceed with our study of chemistry, we will find ourselves thinking in two realms the macroscopic realm of ordinary-sized objects macro = large) and the submicroscopic realm of atoms and molecules. We make our observations in the macroscopic world, but in order to understand that world, we must visualize how atoms and molecules behave at the submicroscopic level. Chemistry is the science that seeks to understand the properties and behavior of matter by studying the properties and behavior of atoms and molecules. 

Well, first of all, there are the ingenious experiments designed to show us that quantum effects can, indeed, appear in the macroscopic realm. In the form of SQUID devices, with their superimposed superconducting currents, such macroscopic quantum devices can become practical measuring instruments. And there are such delicate laboratory experiments such as the preparation of macroscopic collections of atoms in a single degenerate Bose-Einstein state. But now the claim might be that such quantum effects, if not limited to the microscopic, are, perhaps, limited to special, technically prepared situations of scientific artifacts. 

Suppose the absolute value of the charge of the electron was shghtly greater than the charge of a proton. How would matter behave What does this tell you about how small changes in the atomic realm affect the macroscopic realm ... 

The energy is proportional to 1/m. This means that the separation between allowed energy levels decreases as m increases. Ultimately, for a macroscopic object, m is so large that the levels are too closely spaced to be distinguished from the continuum of levels expected in classical mechanics. This is an example of the correspondence principle, which, in its most general form, states that the predictions of quantum mechanics must pass smoothly into those of classical mechanics whenever we progress in a continuous way from the microscopic to the macroscopic realm. 

With time-dependent computer simulation and visualization we can give the novices to QM a direct mind s eye view of many elementary processes. The simulations can include interactive modes where the students can apply forces and radiation to control and manipulate atoms and molecules. They can be posed challenges like trapping atoms in laser beams. These simulations are the inside story of real experiments that have been done, but without the complexity of macroscopic devices. The simulations should preferably be based on rigorous solutions of the time dependent Schrddinger equation, but they could also use proven approximate methods to broaden the range of phenomena to be made accessible to the students. Stationary states and the dynamical transitions between them can be presented as special cases of the full dynamics. All these experiences will create a sense of familiarity with the QM realm. The experiences will nurture accurate intuition that can then be made systematic by the formal axioms and concepts of QM. 

The building blocks of all materials in any phase are atoms and molecules. Their arrangements and how they interact with one another define many properties of the material. The nanotechnology MBBs, because of their sizes of a few nanometers, impart to the nanostructures created from them new and possibly preferred properties and characteristics heretofore unavailable in conventional materials and devices. These nanosize building blocks are intermediate in size, lying between atoms and microscopic and macroscopic systems. These building blocks contain a hmited and countable number of atoms. They constitute the basis of our entry into new realms of bottom-up nanotechnology [97, 98]. 

The nanoscale world is exciting because it is governed by rules differing from those in the macroscopic, or even microscopic, realm. It is a world where quantum mechanics dominates the scene, and events on the single-molecule scale are critical. What we know about the behavior of material on our scale is no longer true on the nanometer scale, and our formularies must be re-written. In order to study this quantum world, a quantum-mechanical probe is essential. Electron tunneling provides that quantum-mechanical tool. 

This lecture exposed these rather revolutionary concepts to an elite scientific community in Europe. Secondly, an invitation by Dr. P. Golitz (Editor, Angew. Chem.) to publish an important review [20] entitled Starburst dendrimers molecular-level control of size, shape, surface chemistry, topology and flexibility from atoms to macroscopic matter provided broad exposure to the basic concepts underlying dendrimer chemistry. Finally, important contributions by key researchers significantly expanded the realm of dendrimer chemistry with the convergent synthesis approach of Frechet and Elawker [37] (Figure 4), as well as the systematic and critical photophysical characterization of Turro et al [38],... 

Our world can be studied at different levels of magnification. At the macroscopic level, matter is large enough to be seen, measured, and handled. A handful of sand and a glass of water are macroscopic samples of matter. At the micro-scopic level, physical structure is so fine that it can be seen only with a microscope. A biological cell is microscopic, as is the detail on a dragonfly s wing. Beyond the microscopic level is the submicroscopic—the realm of atoms and molecules and an important focus of chemistry. 

Classical physics remains an excellent approximation to much of the behaviour of bodies on a macroscopic scale. It is in the microscopic realm that the quantum theory is essential. The behaviour of electrons in atoms and molecules, and the nature of the chemical bond, are among the problems that classical physics is unable to describe. It was only following the development of the quantum theory that chemists could really use physical ideas to provide a satisfactory understanding of their own problems. 

Unless the pressure is so low that the molecular mean free path (Appendix E) is comparable to the dimensions of the chamber enclosing the gas, the rates of the first and last steps, 1 and 5, are governed by molecular diffusion rates (or by rates of mass transfer through a boundary layer, if the gas is in motion). Although these macroscopic transfer processes, which lie within the realm of fluid mechanics (Appendixes C-E), often are the ratedetermining steps [62] (see also Chapter 12), we shall assume here that they are so fast that they can be neglected. 

Progress in the physics of disordered media—that is, in the physics of media with a random distribution of microheterogeneity—is mainly made via the solution of problems involving the connection between the microscopic structure and the macroscopic behavior. This problem properly belongs to the realm of the kinetic theory of matter and is analogous to the problem of locking in the theory of fluids, hydrodynamic turbulence, the theory of phase transitions, and so on. 

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