Chemistry distinctive nature

The marine organic geochemistiy component of chemical oceanography involves the study of ocean systems via analysis of non-living organic substances at the suh-micron size scale (e.g. molecules, atoms and nuclei). As in the field of chemistry, this is a separate branch of marine chemistry because of the complexity of compounds that are studied and the distinct nature of the anal5dical methods used. Organic compounds are important to a wide variety of processes that control marine and environmental chemistiy. For example, approximately half of net photosynthetic production in the sea... 

Chemical education can serve three purposes. First, it can provide a preparation for those who are to conduct research and/or development in chemistry or to staff the production processes of chemical-based industries. Second, it can provide a component of the general education of the population. Third, it can act, to some degree, as an exemplar for the conduct and outcomes of science . However, whatever the purpose addressed, any chemical education provided must be based on a sound understanding of the subject of chemistry itself. The difficulty in following this precept is that the distinctive nature of chemistry has not yet been clearly established. Its boundaries with other subjects, for example physics, biology, earth science, remain fuzzy. The four chapters in this section are each concerned with one aspect of the nature of chemistry that has important implications for chemical education, whatever its purposes. 

The material has been arranged according to didactic needs. Though many textbooks begin with carbohydrates, this seemed to be inappropriate, since the chemistry as well as the biochemistry of carbohydrates is rather complicated. Therefore we begin with simple compounds like amino acids (the introductory chapter on organic chemistry is mainly a short compendium of some relevant facts), and then turn to proteins and to enzyme proteins, leaving the carbohydrates for a later chapter. No distinction has been made between descriptive biochemistry, the chemistry of natural products, and dynamic biochemistry or metabolism. On the contrary, in some chapters the chemical structures of the natural compounds have been deduced from the description of their biosyntheses. 

Thus we find that each of these gases has distinctive properties. If these gases are made up of particles, then the particles must be distinctive. The particles that are present in ammonia cannot be like the particles in hydrogen chloride, or like those in the other gases. The nature of the ammonia particles, then, is the key to the properties of ammonia. The particles that make up a gas determine its chemistry. They are so important to the chemist that they are given a special name. A gas is described as a collection of particles called molecules. 

Clearly kinetics alone will not distinguish the two schemes. To gain this distinction one can deliberately add a reagent that, judging from its independent chemistry, will react with one of the possible chain-carrying radicals. If the suspected radical is indeed an intermediate, and it reacts with the addend, the overall reaction will be slowed or halted. The added substance is a chain-breaker. In this case Fe2+ and Cu2+ (separately) were added. The first of these would very likely react with either of the peroxyl radicals, ROO or MOO. Indeed, Fe2+ dramatically inhibits the reaction. This evidence confirms the chain nature of the process, but does not distinguish between the mechanisms since both ROO and MOO would be scavenged by Fe2+. 

Clean and Polluted Air. In the development of atmospheric chemistry, there has been an historic separation between those studying processes in the natural or unpolluted atmosphere, and those more concerned with air pollution chemistry. As the field has matured, these distinctions have begun to disappear, and with this disappearance has come the realization that few regions of the troposphere are completely unaffected by anthropogenic emissions. An operational definition of clean air could be based upon either the NMHC concentration, or upon the NOjj concentration. 

A striking feature of the cellular automata (CA) models is that they treat not only the ingredients, or agents, of the model as discrete entities, as do the traditional models of physics and chemistry, but now time (iterations) and space (the cells) are also regarded as discrete, in stark contrast to the continuous forms for these parameters assumed in the traditional, equation-based models. In practice, as we shall see, this distinction makes little or no difference, for the traditional continuous results appear, quite naturally, as limiting cases of the discrete CA analyses. Nonetheless, this quantization of time and space does raise some interesting theoretical and philosophical questions, which we shall, however, ignore at this time. ... 

Further error is introduced if reactions distinct from those for which data is available affect the chemistry of a natural fluid. Consider as an example the problem of predicting the silica content of a fluid flowing through a quartz sand aquifer. There is little benefit in modeling the reaction rate for quartz if the more reactive minerals (such as clays and zeolites) in the aquifer control the silica concentration. 

Although orbital hybridizations and molecular shapes for hypovalent metal hydrides of the early transition metals and the normal-valent later transition metals are similar, the M—H bonds of the early metals are distinctly more polar. For example, metal-atom natural charges for YH3 (+1.70), HfH4 (+1.75), and TaHs (+1.23) are all significantly more positive than those (ranging from +0.352 to —0.178) for the homoleptic hydrides from groups 6-10. Indeed, the empirical chemistry of early transition-metal hydrides commonly reveals greater hydricity than does that of the later transition-metal hydrides. 

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