Microscopic world

That s fine in the macroscopic world, but how does the concept of temperature translate to the microscopic world ... 

Each chapter in this book provides many problems of different sorts. The inchapter problems are placed for immediate reinforcement of ideas just learned, while end-of-ebapter problems provide additional practice and are of several types. They begin with a short section called "Visualizing Chemistry," which helps you "see" the microscopic world of molecules and provides practice for working in three dimensions. After the visualizations are many "Additional Problems." Early problems are primarily of the drill type, providing an opportunity for you to practice your command of the fundamentals. Later problems rend to be more thought-provoking, and some are real challenges. 

Nitmerotts examples of chmbing the ladder can be fotmd in textbooks for secondary edncation. For example, textbooks start the stndy of the snbject of salts with the (strb-) microscopic particles of atoms and molectrles, followed by how atoms theoretically ate converted into iotts, and how ionic srrbstances ate brrilt from charged ions. Textbooks continne with the macroscopic properly of the soln-bility of ionic snbstances in water. Snbseqnently mote complex ions, snch as strl-phates and nitrates, ate addressed to become part of the stndents repertoire ns-ing the sub-microscopic world of chemistry and the symbolic representations. For other subjects, such as organic chemistiy, the pathway for stndy from the basic sub-microscopic particles and related chemical principles to making sense of a relevant macro-world of applications (e.g. production of medicines) is very long. Moreover, the sub-microscopic world of state-of-the-art chemistry has become very complex. 

How can the curriculum theory described above be useful in effectively applying the two strategies, cormecting to daily-life experiences and updating chemical content, when trying to improve the meaningfulness of learrring with respect to the relationship between macroscopic phenomerra and the sub-microscopic world of atoms and molecrrles ... 

Harrison, A. G., Treagust, D. E. (2002). The particulate nature of matter challenges in understanding the sub-microscopic world. In J. K. Gilbert, O. de Jong, R. Justi, D. F. Treagust, J. H. van Uriel (Eds.), Chemical education Towards research-based practice (pp. 189-212). Dordecht Kluwer Academic Publishers. 

Kinetics provides the frame vork for describing the rate at which a chemical reaction occurs and enables us to relate the rate to a reaction mechanism that describes how the molecules react via intermediates to the eventual product. It also allows us to relate the rate to macroscopic process parameters such as concentration, pressures, and temperatures. Hence, kinetics provides us with the tools to link the microscopic world of reacting molecules to the macroscopic world of industrial reaction engineering. Obviously, kinetics is a key discipline for catalysis. 

Symmetry breaking is a universal phenomenon, from eosmology to the microscopic world, a perfectly familiar and daily experience whien should not generate the reluctance that it induces in some domains of Physics, and especially in Quantum Chemistry. In elassieal physics, the symmetry breaking of an a-priori symmetrical problem is sometimes refered to as the lack of symmetry of the initial conditions. But it may be a deeper phenomenon, the symmetry-broken solutions being more stable than the symmetrical one. 

A production chemist is interested primarily in the macroscopic world, not the microscopic one of atoms and molecules. Even a chemistry student working in the laboratory will not be weighing out individual atoms and molecules, but large numbers of them in grams. There must be a way to bridge the gap between the microscopic world of individual atoms and molecules, and the macroscopic world of grams and kilograms. There is—it is called the mole concept, and it is one of the central concepts in the world of chemistry. 

The mole (mol) is the amount of a substance that contains the same number of particles as atoms in exactly 12 grams of carbon-12. This number of particles (atoms or molecules or ions) per mole is called Avogadro s number and is numerically equal to 6.022 x 1023 particles. The mole is simply a term that represents a certain number of particles, like a dozen or a pair. That relates moles to the microscopic world, but what about the macroscopic world The mole also represents a certain mass of a chemical substance. That mass is the substance s atomic or molecular mass expressed in grams. In Chapter 5, the Basics chapter, we described the atomic mass of an element in terms of atomic mass units (amu). This was the mass associated with an individual atom. Then we described how one could calculate the mass of a compound by simply adding together the masses, in amu, of the individual elements in the compound. This is still the case, but at the macroscopic level the unit of grams is used to represent the quantity of a mole. Thus, the following relationships apply ... 

The microscopic world of atoms is difficult to imagine, let alone visualize in detail. Chemists and chemical engineers employ different molecular modelling tools to study the structure, properties, and reactivity of atoms, and the way they bond to one another. Richard Bader, a chemistry professor at McMaster University, has invented an interpretative theory that is gaining acceptance as an accurate method to describe molecular behaviour and predict molecular properties. According to Dr. Bader, shown below, small molecules are best represented using topological maps, where contour lines (which are commonly used to represent elevation on maps) represent the electron density of molecules. 

The little man, or homunculus, as it was sometimes called, was imaginative, of course—the mind sometimes creates such illusions when examining an object too small or fuzzy to be clearly seen. The notion that the microscopic world consisted of familiar objects reduced to a small scale was also incorrect. As scientists probed the nature of particles, they realized that the behavior of small objects does not necessarily mimic larger ones. This discovery opened up new vistas in science as well as technology, including the subject of this chapter—technology on the scale of atoms and molecules. 

Canter-Lund, H., and Lund, J. W. G. (1995) Freshwater Algae Their Microscopic World Explored, Biopress, Bristol, England... 

Waldrop, MM Mewing the Universe as a Coat of Chain Mail New Calculations Have Pointed the Way to Quantum Gravity and Suggested a Novel Structure for the Sub sub Microscopic World, Science, 1510 (December 14. 1990). 

Chapter 5 gives a microscopic-world explanation of the second law, and uses Boltzmann s definition of entropy to derive some elementary statistical mechanics relationships. These are used to develop the kinetic theory of gases and derive formulas for thermodynamic functions based on microscopic partition functions. These formulas are apphed to ideal gases, simple polymer mechanics, and the classical approximation to rotations and vibrations of molecules. 

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. 

Quantum mechanics, the modem description of the microscopic world, also conserves energy. 

G. Hallegraeff, Plankton A Microscopic World, CSIRO/Robert Brown and Assocs., Melbourne, 1988. 

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