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General Chemistry Principles, Patterns, and Applications, 2011

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. LDPE<br />

c. HDPE<br />

d. LDPE<br />

Summary<br />

Polymers are giant molecules that consist of long chains of units calledmonomers connected by<br />

covalent bonds. Polymerization is the process of linking monomers together to form a<br />

polymer. Plastic is the property of a material that allows it to be molded. Biological polymers formed<br />

from amino acid residues are called peptides or proteins, depending on their size. Enzymes are<br />

proteins that catalyze a biological reaction. A particle that is more than a hundred times longer than it is<br />

wide is a fiber, which can be formed by a high-temperature decomposition reaction called pyrolysis.<br />

K E Y T A K E A W A Y<br />

<br />

Polymers are giant molecules formed from addition or condensation reactions <strong>and</strong> can<br />

be classified as either biological or synthetic polymers.<br />

C O N C E PTUAL P R OBLEMS<br />

1. How are amino acids <strong>and</strong> proteins related to monomers <strong>and</strong> polymers? Draw the general structure of an<br />

amide bond linking two amino acid residues.<br />

2. Although proteins <strong>and</strong> synthetic polymers (such as nylon) both contain amide bonds, different terms are used<br />

to describe the two types of polymer. Compare <strong>and</strong> contrast the terminology used for the<br />

a. smallest repeating unit.<br />

b. covalent bond connecting the units.<br />

12.9 Contemporary Materials<br />

L E A R N I N G O B JE C T I V E<br />

1. To become familiar with the properties of some contemporary materials.<br />

In addition to polymers, other materials, such as ceramics, high-strength alloys, <strong>and</strong> composites, play a major role in<br />

almost every aspect of our lives. Until relatively recently, steel was used for any application that required an especially<br />

strong <strong>and</strong> durable material, such as bridges, automobiles, airplanes, golf clubs, <strong>and</strong> tennis rackets. In the last 15 to<br />

20 years, however, graphite or boron fiber golf clubs <strong>and</strong> tennis rackets have made wood <strong>and</strong> steel obsolete for these<br />

items. Likewise, a modern jet engine now is largely composed of Ti <strong>and</strong> Ni by weight rather than steel (). The<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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