Chem 101 Chapter 13- Intermolecular Forces, Liquids, and Solids

Chem 101 Chapter 13- Intermolecular Forces, Liquids, and Solids

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The Mystery of the Disappearing Fingerprints The events of September 11, 2001, are etched in everyone’s memory. The specter of domestic terrorism, however, was first raised almost two years earlier. That’s when a man was apprehended in December 1999 at the U.S.–Canadian border with bomb materials and a map of Los Angeles International Airport. Although he claimed innocence, his fingerprints were on the bomb materials, and he was convicted of an attempt to bomb the airport. Each of us has a unique fingerprint pattern, as first described by John Purkinji in 1823. Not long after his discovery, English colonists in India began using fingerprints on contracts because they believed it made the contract appear more binding. Not until late in the 19th century, however, was fingerprinting used as an identifier. Sir Francis Galton, a British anthropologist and a cousin of Charles Darwin, established that a person’s fingerprints do not 13 Intermolecular Forces, Liquids, and Solids Charles D. Winters States of Matter Taking an official fingerprint at the local police station. 588 Charles D. Winters Dusting for fingerprints on a glass coffee mug.
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589 Chapter Outline 13.1 States of Matter and the Kinetic-Molecular Theory 13.2 Intermolecular Forces 13.3 Hydrogen Bonding 13.4 Summary of Intermolecular Forces 13.5 Properties of Liquids 13.6 The Solid State: Metals 13.7 The Solid State: Structures and Formulas of Ionic Solids 13.8 Other Kinds of Solid Materials 13.9 The Physical Properties of Solids 13.10 Phase Diagrams Chapter Goals See Chapter Goals Revisited (page 633). Test your knowl- edge of these goals by taking the exam-prep quiz on the General ChemistryNow CD-ROM or website. Describe intermolecular forces and their effects. Understand the importance of hydrogen bonding. Understand the properties of liquids. Understand cubic unit cells. Relate unit cells for ionic compounds to formulas. Describe the properties of solids. Understand the nature of phase diagrams. Scientists at Oak Ridge National Laboratory studied the fingerprints of 50 child and adult volunteers, identifying the compounds present by such techniques as mass spectrometry [ page 127]. What they found clarified the mystery of the disappearing fingerprints. Children’s fingerprints contain more low-molecular-weight fatty acids than do adult fingerprints. (Fatty acids consist of a carbon– hydrogen chain with a carboxylic acid group, CO 2 H, at one end. See page 505.) Due to the relatively low molecular weight and low polarity of these acids, their intermolecular forces are weak and the compounds are volatile. As a consequence, children’s fingerprints simply evaporate. In contrast, adult fingerprints contain esters of long-chain fatty acids with long-chain alcohols. These are waxes, semisolid or solid organic compounds with high molecular weights and low volatility. Examples of waxes are lanolin, a component of wool, and the carnuba wax used in furniture polish.
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