Explanation of Concepts

Thermal degradation is defined as degradation at elevated temperatures in the absence of oxygen. Degradation rates and specific reaction mechanisms of thermal degradation depend on the structure of the plastics and the temperature. Thermal- 

Thermal resistance of plastics in the absence of other active substances is proportional to the dissociation energy of the various chemical bonds, s. Table 1.7. 

Thermal resistance is often tested under pyrolytic conditions. Here, sufficient energy is added to cleave primary bonds in the polymers. Most decomposition phenomena under these conditions are influenced by the basic plastics structure and not by traces of impurities, although the order of decomposition rates and activation energies is influenced by the chromophores present. The pyrolysis test results for polymers are summarized in Table 5.38 [31]. 

Some plastics, such as polymethyl methacrylate, decompose under thermal exposure into their monomers. Other plastics, such as polypropylene, generally form an entire spectrum of decomposition products. 

Based on pyrolysis tests, the following order of bond stability can be established C-F C-H C-C C-C1 

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The theory sections consist of explanations of concepts in or related to the research discussed in the module. They are structured to parallel the content of the videos, allowing easy access for students while watching the videos. The format of the information is similar to a textbook, with written explanations accompanied by appropriate schematics, figures, and equations. The theory pages are stored as HTML in an XML repository, accessible only through the enhanced interface. 

Yet another way to use this textbook is to use polymers as the examples for discussions or explanation of concepts covered in a chemistry course. Chapter 1 can be used in conjunction with the first chapter of any textbook where a discussion of What is chemistry occurs. A teacher wants students to know the importance of chemistry in their everyday lives and the good things that have been the result of chemistry, but it is also necessary to discuss some of the problems that have arisen because of the careless use of chemistry. (You can also refer to Chapter 9, Disposal, Degradation, And Recycling Bioplastics, for another angle on responsible chemistry.)... 

Because this is a review chapter, it does not follow my usual format. Normally, I have you, the reader, perform a few simple activities before reading explanations of concepts. The explanations use the results of the activities to help you anchor the concepts to experiences, thus leading to a deeper understanding than would otherwise be possible. If I did the activity thing in this chapter, then this chapter would be as long as the first book, and that wouldnT make much sense. So, what follows here are explanations of concepts sans activities. 

It is our hope that this book, through its careful explanations of concepts and its use of numerous practical examples and figures, helps the students develop the necessary skills to bridge the gap between knowledge and the confidence for proper application of that knowledge. 

Developmental Review Over the past four years, a team of development editors, including line editors and art editors, have worked with the author to hone his distinctive voice, test explanation of concepts in the classroom, and confirm that the pedagogy was consistent and added value to the learning process. 

Explanations of concepts without mathematics and with easy-to-understand physical/ chemical science concepts... 

We used the concept of sound velocity dispersion for explanation of the shift of pulse energy spectrum maximum, transmitted through the medium, and correlation of the shift value with function of medium heterogeneity. This approach gives the possibility of mathematical simulation of the influence of both medium parameters and ultrasonic field parameters on the nature of acoustic waves propagation in a given medium. 

More information on noncommercially available ferrites can be found in the Hterature (4,24). Extended reviews on soft (4,24—29) and hard (4,29—32) ferrites are also available. Explanations of magnetic concepts used in this article, such as permeabiHty and coercivity, may be found in magnetism textbooks. 

The field of metaHurgy has a unique and frequently very specialized vocabulary. Understanding this language helps to clarify certain concepts and processing steps. A complete dictionary of mining, mineral, and related terms has been compiled (2). The definitions and explanations of key terms foHow. 

An explanation of roles and the advantages of applying the concept of roles in a quality system is given in the ISO 9000 Quality System Development Handbook by David Hoyle (Butterworth-Heinemann, 1998). 

Modern concepts have been extended to the chemistry of heterocyclic compounds more slowly than to the chemistry of aromatic and aliphatic systems, but efforts are now being made to classify and explain the properties and reactions of heterocyclic compounds in terms of these newer ideas (cf. reference 11). However, many of the most important heterocyclic compounds are potentially tautomeric, and elucidation of their tautomeric composition must precede a logical treatment of their properties. Further, many natural products such as the nucleic acids and alkaloids contain potentially tautomeric groups and information of this type is needed for a detailed explanation of th reactions which they undergo,... 

Each chapter contains a Chemistry Beyond the Classroom feature. It is a self-contained essay that illustrates a current example either of chemistry in use in the world or an area of chemical research. It does not intrude into the explanation of the concepts, so it won t distract you. But we promise that those essays—if you read them—will make you more scientifically literate. 

ABSTRACT This article concerns various foundational aspects of the periodic system of the elements. These issues include the dual nature of the concept of an "element" to include element as a "basic substance" and as a "simple substance." We will discuss the question of whether there is an optimal form of the periodic table, including whether the left-step table fulfils this role. We will also discuss the derivation or explanation of the [n + , n] or Madelung rule for electron-shell filling and whether indeed it is important to attempt to derive this rule from first principles. In particular, we examine the views of two chemists, Henry Bent and Eugen Schwarz, who have independently addressed many of these issues. 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109 959-971, 2009... 

The qualitative thermodynamic explanation of the shielding effect produced by the bound neutral water-soluble polymers was summarized by Andrade et al. [2] who studied the interaction of blood with polyethylene oxide (PEO) attached to the surfaces of solids. According to their concept, one possible component of the passivity may be the low interfacial free energy (ysl) of water-soluble polymers and their gels. As estimated by Matsunaga and Ikada [3], it is 3.7 and 3.1 mJ/m2 for cellulose and polyvinylalcohol whereas 52.6 and 41.9 mJ/m2 for polyethylene and Nylon 11, respectively. Ikada et al. [4] also found that adsorption of serum albumin increases dramatically with the increase of interfacial free energy of the polymer contacting the protein solution. 

Once they have detected patterns, scientists develop hypotheses, possible explanations of the laws—or the observations—in terms of more fundamental concepts. Observation requires careful attention to detail, but the development of a hypothesis requires insight, imagination, and creativity. In 1807, John Dalton interpreted experimental results to propose the hypothesis that matter consists of atoms. Although Dalton could not see individual atoms, he was able to imagine them and formulate his atomic hypothesis. Dalton s hypothesis was a monumental insight that helped others understand the world in a new way. The process of scientific discovery never stops. With luck and application, you may acquire that kind of insight as you read through this text, and one day you may make your own extraordinary hypotheses. 

The coordination theory and the principles governing coordinated structures provide the foundation for an interpretation of the structure of the complex silicates and other complex ionic crystals which may ultimately lead to the understanding of the nature and the explanation of the properties of these interesting substances. This will be achieved completely only after the investigation of the structures of many crystals with x-rays. To illustrate the clarification introduced by the new conception the following by no means exhaustive examples are discussed. 

Understanding how chemistry and chemistry-based technologies relate to each other. Whilst chemistry seeks to produce explanations of the natural world, chemical technologies seek to change that world. The concepts and models produced by these two fields have a strong interrelation and therefore influence each other ... 

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