principles of general chemistry v1 0

The study of matter and the changes that material substances undergo.. Figure 1.1 Chemistry in Everyday Life Although most people do not recognize it, chemistry and chemical compounds ar

Principles of General

Chemistry

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About the Authors 1

Acknowledgments 4

Dedication 5

Preface 6

Chapter 1: Introduction to Chemistry 9

Chemistry in the Modern World 11

The Scientific Method 17

A Description of Matter 26

A Brief History of Chemistry 46

The Atom 58

Isotopes and Atomic Masses 69

Introduction to the Periodic Table 85

Essential Elements for Life 93

Essential Skills 1 98

End-of-Chapter Material 118

Chapter 2: Molecules, Ions, and Chemical Formulas 123

Chemical Compounds 125

Chemical Formulas 150

Naming Ionic Compounds 166

Naming Covalent Compounds 183

Acids and Bases 211

Industrially Important Chemicals 223

End-of-Chapter Material 235

Chapter 3: Chemical Reactions 238

The Mole and Molar Masses 240

Determining Empirical and Molecular Formulas 261

Chemical Equations 291

Mass Relationships in Chemical Equations 309

Classifying Chemical Reactions 338

Chemical Reactions in the Atmosphere 368

Essential Skills 2 381

End-of-Chapter Material 390

Solution Concentrations 419

Stoichiometry of Reactions in Solution 439

Ionic Equations 453

Precipitation Reactions 459

Acid–Base Reactions 473

The Chemistry of Acid Rain 502

Oxidation–Reduction Reactions in Solution 509

Quantitative Analysis Using Titrations 531

Essential Skills 3 544

End-of-Chapter Material 552

Chapter 5: Energy Changes in Chemical Reactions 559

Energy and Work 561

Enthalpy 576

Calorimetry 621

Thermochemistry and Nutrition 641

Energy Sources and the Environment 654

Essential Skills 4 671

End-of-Chapter Material 680

Chapter 6: The Structure of Atoms 685

Waves and Electromagnetic Radiation 687

The Quantization of Energy 697

Atomic Spectra and Models of the Atom 709

The Relationship between Energy and Mass 732

Atomic Orbitals and Their Energies 746

Building Up the Periodic Table 773

End-of-Chapter Material 796

Chapter 7: The Periodic Table and Periodic Trends 802

The History of the Periodic Table 804

Sizes of Atoms and Ions 815

Energetics of Ion Formation 833

The Chemical Families 867

Trace Elements in Biological Systems 893

End-of-Chapter Material 901

Ionic Bonding 908

Lattice Energies in Ionic Solids 916

Lewis Electron Dot Symbols 937

Lewis Structures and Covalent Bonding 942

Exceptions to the Octet Rule 978

Lewis Acids and Bases 988

Properties of Covalent Bonds 995

Polar Covalent Bonds 1009

End-of-Chapter Material 1021

Chapter 9: Molecular Geometry and Covalent Bonding Models 1025

Predicting the Geometry of Molecules and Polyatomic Ions 1027

Localized Bonding and Hybrid Atomic Orbitals 1069

Delocalized Bonding and Molecular Orbitals 1090

Polyatomic Systems with Multiple Bonds 1134

End-of-Chapter Material 1149

Chapter 10: Gases 1154

Gaseous Elements and Compounds 1156

Gas Pressure 1165

Relationships among Pressure, Temperature, Volume, and Amount 1181

The Ideal Gas Law 1191

Mixtures of Gases 1219

Gas Volumes and Stoichiometry 1230

The Kinetic Molecular Theory of Gases 1241

The Behavior of Real Gases 1265

Essential Skills 5 1278

End-of-Chapter Material 1284

Intermolecular Forces 1297

Unique Properties of Liquids 1320

Vapor Pressure 1334

Changes of State 1351

Critical Temperature and Pressure 1370

Phase Diagrams 1377

Liquid Crystals 1386

Essential Skills 6 1395

End-of-Chapter Material 1400

Chapter 12: Solids 1403

Crystalline and Amorphous Solids 1405

The Arrangement of Atoms in Crystalline Solids 1412

Structures of Simple Binary Compounds 1426

Defects in Crystals 1442

Correlation between Bonding and the Properties of Solids 1463

Bonding in Metals and Semiconductors 1476

Superconductors 1494

Polymeric Solids 1503

Contemporary Materials 1511

End-of-Chapter Material 1521

Chapter 13: Solutions 1525

Factors Affecting Solution Formation 1527

Solubility and Molecular Structure 1539

Units of Concentration 1559

Effects of Temperature and Pressure on Solubility 1577

Colligative Properties of Solutions 1590

Aggregate Particles in Aqueous Solution 1630

End-of-Chapter Material 1639

Reaction Rates and Rate Laws 1656

Methods of Determining Reaction Order 1679

Using Graphs to Determine Rate Laws, Rate Constants, and Reaction Orders 1713

Half-Lives and Radioactive Decay Kinetics 1721

Reaction Rates—A Microscopic View 1735

The Collision Model of Chemical Kinetics 1749

Catalysis 1765

End-of-Chapter Material 1776

Chapter 15: Chemical Equilibrium 1785

The Concept of Chemical Equilibrium 1787

The Equilibrium Constant 1794

Solving Equilibrium Problems 1826

Nonequilibrium Conditions 1852

Factors That Affect Equilibrium 1869

Controlling the Products of Reactions 1891

Essential Skills 1900

End-of-Chapter Material 1903

Chapter 16: Aqueous Acid–Base Equilibriums 1911

The Autoionization of Water 1913

A Qualitative Description of Acid–Base Equilibriums 1926

Molecular Structure and Acid–Base Strength 1959

Quantitative Aspects of Acid–Base Equilibriums 1971

Acid–Base Titrations 2000

Buffers 2031

End-of-Chapter Material 2059

Chapter 17: Solubility and Complexation Equilibriums 2063

Determining the Solubility of Ionic Compounds 2065

Factors That Affect Solubility 2087

The Formation of Complex Ions 2094

Solubility and pH 2112

Qualitative Analysis Using Selective Precipitation 2131

End-of-Chapter Material 2136

The First Law of Thermodynamics 2155

The Second Law of Thermodynamics 2170

Entropy Changes and the Third Law of Thermodynamics 2191

Free Energy 2204

Spontaneity and Equilibrium 2228

Comparing Thermodynamics and Kinetics 2244

Thermodynamics and Life 2253

End-of-Chapter Material 2266

Chapter 19: Electrochemistry 2273

Describing Electrochemical Cells 2275

Standard Potentials 2292

Comparing Strengths of Oxidants and Reductants 2322

Electrochemical Cells and Thermodynamics 2332

Commercial Galvanic Cells 2366

Corrosion 2378

Electrolysis 2388

End-of-Chapter Material 2404

Chapter 20: Nuclear Chemistry 2411

The Components of the Nucleus 2413

Nuclear Reactions 2426

The Interaction of Nuclear Radiation with Matter 2458

Thermodynamic Stability of the Atomic Nucleus 2473

Applied Nuclear Chemistry 2494

The Origin of the Elements 2510

End-of-Chapter Material 2521

Chapter 21: Periodic Trends and the s-Block Elements 2525

Overview of Periodic Trends 2527

The Chemistry of Hydrogen 2539

The Alkali Metals (Group 1) 2552

The Alkaline Earth Metals (Group 2) 2579

The s-Block Elements in Biology 2598

End-of-Chapter Material 2608

The Elements of Group 14 2638

The Elements of Group 15 (The Pnicogens) 2663

The Elements of Group 16 (The Chalcogens) 2684

The Elements of Group 17 (The Halogens) 2703

The Elements of Group 18 (The Noble Gases) 2718

End-of-Chapter Material 2731

Chapter 23: The d-Block Elements 2736

General Trends among the Transition Metals 2737

A Brief Survey of Transition-Metal Chemistry 2749

Metallurgy 2777

Coordination Compounds 2788

Crystal Field Theory 2813

Transition Metals in Biology 2837

End-of-Chapter Material 2862

Chapter 24: Organic Compounds 2866

Functional Groups and Classes of Organic Compounds 2868

Isomers of Organic Compounds 2873

Reactivity of Organic Molecules 2898

Common Classes of Organic Reactions 2906

Common Classes of Organic Compounds 2919

The Molecules of Life 2951

End-of-Chapter Material 2966

Appendix A: Standard Thermodynamic Quantities for Chemical Substances at 25°C 2971

Appendix B: Solubility-Product Constants (Ksp) for Compounds at 25°C 2984

Appendix C: Dissociation Constants and pKa Values for Acids at 25°C 2990

Appendix D: Dissociation Constants and pKb Values for Bases at 25°C 2993

Appendix E: Standard Reduction Potentials at 25°C 2994

Appendix F: Properties of Water 3001

Appendix G: Physical Constants and Conversion Factors 3003

Appendix H: Periodic Table of Elements 3005

Appendix I: Experimentally Measured Masses of Selected Isotopes 3012

Photo Credits 3016

Bruce A Averill

Bruce A Averill grew up in New England He then received his B.S with high honors

in chemistry at Michigan State University in 1969, and his Ph.D in inorganic

chemistry at MIT in 1973 After three years as an NIH and NSF Postdoctoral Fellow

at Brandeis University and the University of Wisconsin, he began his independentacademic career at Michigan State University in 1976

He was promoted in 1982, after which he moved to the University of Virginia, where

he was promoted to Professor in 1988 In 1994, Dr Averill moved to the University

of Amsterdam in the Netherlands as Professor of Biochemistry He then returned tothe United States to the University of Toledo in 2001, where he was a DistinguishedUniversity Professor He was then named a Jefferson Science Policy Fellow at theU.S State Department, where he remained for several years as a senior energyconsultant He is currently the founder and senior partner of Stategic EnergySecurity Solutions, which creates public/private partnerships to ensure globalenergy security Dr Averill’s academic research interests are centered on the role ofmetal ions in biology He is also an expert on cyber-security

In his European position, Dr Averill headed a European Union research networkcomprised of seven research groups from seven different European countries and astaff of approximately fifty research personnel In addition, he was responsible forthe research theme on Biocatalysis within the E C Slater Institute of the University

of Amsterdam, which consisted of himself as head and a team of 21 professionals,ranging from associate professors to masters students at any given time

Dr Averill’s research has attracted a great deal of attention in the scientific

community His published work is frequently cited by other researchers, and he hasbeen invited to give more than 100 presentations at educational and researchinstitutions and at national and international scientific meetings Among his

numerous awards, Dr Averill has been an Honorary Woodrow Wilson Fellow, anNSF Predoctoral Fellow, an NIH and NSF Postdoctoral Fellow, and an Alfred P SloanFoundation Fellow; he has also received an NSF Special Creativity Award

Over the years, Dr Averill has published more than 135 articles dealing with

chemical, physical, and biological subjects in refereed journals, and he has alsopublished 15 chapters in books and more than 80 abstracts from national and

international meetings In addition, he has co-edited a graduate text on catalysis,and he has taught courses at all levels, including general chemistry, biochemistry,advanced inorganic, and physical methods.

Aside from his research program, Dr Averill is an enthusiastic sailor and an avidreader He also enjoys traveling with his family, and at some point in the future hewould like to sail around the world in a classic wooden boat

Patricia Eldredge

Patricia Eldredge was raised in the U.S diplomatic service, and has traveled andlived around the world She has degrees from the Ohio State University, theUniversity of Central Florida, the University of Virginia, and the University of NorthCarolina, Chapel Hill, where she obtained her Ph.D in inorganic chemistry

following several years as an analytical research chemist in industry In addition,she has advanced offshore sailing qualifications from both the Royal YachtingAssociation in Britain and the American Sailing Association

In 1989, Dr Eldredge was named the Science Policy Fellow for the AmericanChemical Society While in Washington, D.C., she examined the impact of changes infederal funding priorities on academic research funding She was awarded a

Postdoctoral Research Fellowship with Oak Ridge Associated Universities, workingwith the U.S Department of Energy on heterogeneous catalysis and coal

liquefaction Subsequently, she returned to the University of Virginia as a ResearchScientist and a member of the General Faculty

In 1992, Dr Eldredge relocated to Europe for several years While there, she studiedadvanced Maritime Engineering, Materials, and Oceanography at the University ofSouthampton in England, arising from her keen interest in naval architecture

Upon her return to the United States in 2002, she was a Visiting Assistant Professorand a Senior Research Scientist at the University of Toledo Her research interestsincluded the use of protein scaffolds to synthesize biologically relevant clusters Dr.Eldredge has published more than a dozen articles dealing with synthetic inorganicchemistry and catalysis, including several seminal studies describing new syntheticapproaches to metal-sulfur clusters She has also been awarded a patent for herwork on catalytic coal liquefaction

Her diverse teaching experience includes courses on chemistry for the life sciences,introductory chemistry, general, organic, and analytical chemistry When not

authoring textbooks, Dr Eldredge enjoys traveling, offshore sailing, politicalactivism, and caring for her Havanese dogs.

The authors would like to thank the following individuals who reviewed the textand whose contributions were invaluable in shaping the product:

• Rebecca Barlag, Ohio University

• Greg Baxley, Cuesta College

• Karen Borgsmiller, Hood College

• Simon Bott, University of Houston

• David Burgess, Rivier College

• William Bushey, St Marks High School and Delaware Technical JuniorCollege

• Li-Heng Chen, Aquinas College

• Jose Conceicao, Metropolitan Community College

• Rajeev Dabke, Columbus State University

• Michael Denniston, Georgia Perimeter College

• Nathanael Fackler, Nebraska Wesleyan University

• James Fisher, Imperial Valley College

• Brian Gilbert, Linfield College

• Boyd Goodson, Southern Illinois University, Carbondale

• Karin Hassenrueck, California State University, Northridge

• James Hill, California State University, Sacramento

• Robert Holdar, North Lake College

• Roy Kennedy, Massachusetts Bay Community College

• Kristina Knutson, Georgia Perimeter College

• Chunmei Li, University of California, Berkeley

• Eric Malina, University of Nebraska

• Laura McCunn-Jordan, Marshall University

• Giovanni Meloni, University of San Francisco

• Mark Ott, Jackson Community College

• Robert Pike, The College of William & Mary

To Harvey, who opened the door

and to the Virginia Tech community for its resilience and strength We Remember

In this new millenium, as the world faces new and extreme challenges, the

importance of acquiring a solid foundation in chemical principles has becomeincreasingly important to understand the challenges that lie ahead Moreover, asthe world becomes more integrated and interdependent, so too do the scientificdisciplines The divisions between fields such as chemistry, physics, biology,

environmental sciences, geology, and materials science, among others, have

become less clearly defined The goal of this text is to address the increasing closerelationship among various disciplines and to show the relevance of chemistry tocontemporary issues in a pedagogically approachable manner

Because of the enthusiasm of the majority of first-year chemistry students forbiologically and medically relevant topics, this text uses an integrated approachthat includes explicit discussions of biological and environmental applications ofchemistry Topics relevant to materials science are also introduced to meet themore specific needs of engineering students To facilitate integration of such

material, simple organic structures, nomenclature, and reactions are introducedvery early in the text, and both organic and inorganic examples are used whereverpossible This approach emphasizes the distinctions between ionic and covalentbonding, thus enhancing the students’ chance of success in the organic chemistrycourse that traditionally follows general chemistry

The overall goal is to produce a text that introduces the students to the relevanceand excitement of chemistry Although much of first-year chemistry is taught as aservice course, there is no reason that the intrinsic excitement and potential ofchemistry cannot be the focal point of the text and the course We emphasize thepositive aspects of chemistry and its relationship to students’ lives, which requiresbringing in applications early and often Unfortunately, one cannot assume thatstudents in such courses today are highly motivated to study chemistry for its ownsake The explicit discussion of biological, environmental, and materials issues from

a chemical perspective is intended to motivate the students and help them

appreciate the relevance of chemistry to their lives Material that has traditionallybeen relegated to boxes, and thus perhaps perceived as peripheral by the students,has been incorporated into the text to serve as a learning tool

To begin the discussion of chemistry rapidly, the traditional first chapter

introducing units, significant figures, conversion factors, dimensional analysis, and

so on, has been reorganized The material has been placed in the chapters wherethe relevant concepts are first introduced, thus providing three advantages: it

eliminates the tedium of the traditional approach, which introduces mathematicaloperations at the outset, and thus avoids the perception that chemistry is amathematics course; it avoids the early introduction of operations such aslogarithms and exponents, which are typically not encountered again for severalchapters and may easily be forgotten when they are needed; and third, it provides areview for those students who have already had relatively sophisticated high schoolchemistry and math courses, although the sections are designed primarily forstudents unfamiliar with the topic.

Our specific objectives include the following:

1 To write the text at a level suitable for science majors, but using a lessformal writing style that will appeal to modern students

2 To produce a truly integrated text that gives the student who takes

only a single year of chemistry an overview of the most importantsubdisciplines of chemistry, including organic, inorganic, biological,materials, environmental, and nuclear chemistry, thus emphasizingunifying concepts

3 To introduce fundamental concepts in the first two-thirds of thechapter, then applications relevant to the health sciences or engineers.This provides a flexible text that can be tailored to the specific needsand interests of the audience

4 To ensure the accuracy of the material presented, which is enhanced

by the author’s breadth of professional experience and experience asactive chemical researchers

5 To produce a spare, clean, uncluttered text that is less distracting tothe student, where each piece of art serves as a pedagogical device

6 To introduce the distinction between ionic and covalent bonding andreactions early in the text, and to continue to build on this foundation

in the subsequent discussion, while emphasizing the relationshipbetween structure and reactivity

7 To utilize established pedagogical devices to maximize students’ ability

to learn directly from the text These include copious worked examples

in the text, problem-solving strategies, and similar unworked exerciseswith solutions End-of-chapter problems are designed to ensure thatstudents have grasped major concepts in addition to testing theirability to solve numerical, problems Problems emphasizingapplications are drawn from many disciplines

8 To emphasize an intuitive and predictive approach to problem solvingthat relies on a thorough understanding of key concepts and

recognition of important patterns rather than on memorization Manypatterns are indicated throughout the text as notes in the margin

The text is organized by units that discuss introductory concepts, atomic andmolecular structure, the states of matter, kinetics and equilibria, and descriptiveinorganic chemistry The text breaks the traditional chapter on liquids and solidsinto two to expand the coverage of important and topics such as semiconductorsand superconductors, polymers, and engineering materials.

In summary, this text represents a step in the evolution of the general chemistrytext toward one that reflects the increasing overlap between chemistry and otherdisciplines Most importantly, the text discusses exciting and relevant aspects ofbiological, environmental, and materials science that are usually relegated to thelast few chapters, and it provides a format that allows the instructor to tailor theemphasis to the needs of the class By the end ofChapter 6 "The Structure ofAtoms", the student will have already been introduced to environmental topicssuch as acid rain, the ozone layer, and periodic extinctions, and to biological topicssuch as antibiotics and the caloric content of foods Nonetheless, the new material

is presented in such a way as to minimally perturb the traditional sequence oftopics in a first-year course, making the adaptation easier for instructors

Introduction to Chemistry

As you begin your study of college chemistry, those of you who do not intend tobecome professional chemists may well wonder why you need to study chemistry.You will soon discover that a basic understanding of chemistry is useful in a widerange of disciplines and career paths You will also discover that an understanding

of chemistry helps you make informed decisions about many issues that affect you,your community, and your world A major goal of this text is to demonstrate theimportance of chemistry in your daily life and in our collective understanding ofboth the physical world we occupy and the biological realm of which we are a part.The objectives of this chapter are twofold: (1) to introduce the breadth, the

importance, and some of the challenges of modern chemistry and (2) to presentsome of the fundamental concepts and definitions you will need to understand howchemists think and work

An atomic corral for electrons A corral of 48 iron atoms (yellow-orange) on a smooth copper surface

(cyan-purple) confines the electrons on the surface of the copper, producing a pattern of “ripples” in the distribution of the electrons Scientists assembled the 713-picometer-diameter corral by individually positioning iron atoms with the tip of a scanning tunneling microscope (Note that 1 picometer is equivalent to 1 × 10 -12 meters.)

1.1 Chemistry in the Modern World

L E A R N I N G O B J E C T I V E

1 To recognize the breadth, depth, and scope of chemistry

Chemistry1is the study of matter and the changes that material substancesundergo Of all the scientific disciplines, it is perhaps the most extensivelyconnected to other fields of study Geologists who want to locate new mineral or oildeposits use chemical techniques to analyze and identify rock samples

Oceanographers use chemistry to track ocean currents, determine the flux ofnutrients into the sea, and measure the rate of exchange of nutrients betweenocean layers Engineers consider the relationships between the structures and theproperties of substances when they specify materials for various uses Physiciststake advantage of the properties of substances to detect new subatomic particles.Astronomers use chemical signatures to determine the age and distance of stars andthus answer questions about how stars form and how old the universe is The entiresubject of environmental science depends on chemistry to explain the origin andimpacts of phenomena such as air pollution, ozone layer depletion, and globalwarming

The disciplines that focus on living organisms and their interactions with thephysical world rely heavily onbiochemistry2, the application of chemistry to thestudy of biological processes A living cell contains a large collection of complexmolecules that carry out thousands of chemical reactions, including those that arenecessary for the cell to reproduce Biological phenomena such as vision, taste,smell, and movement result from numerous chemical reactions Fields such asmedicine, pharmacology, nutrition, and toxicology focus specifically on how thechemical substances that enter our bodies interact with the chemical components

of the body to maintain our health and well-being For example, in the specializedarea of sports medicine, a knowledge of chemistry is needed to understand whymuscles get sore after exercise as well as how prolonged exercise produces theeuphoric feeling known as “runner’s high.”

Examples of the practical applications of chemistry are everywhere (Figure 1.1

"Chemistry in Everyday Life") Engineers need to understand the chemicalproperties of the substances when designing biologically compatible implants forjoint replacements or designing roads, bridges, buildings, and nuclear reactors that

do not collapse because of weakened structural materials such as steel and cement

1 The study of matter and the

changes that material

substances undergo.

2 The application of chemistry to

the study of biological

processes.

Archaeology and paleontology rely on chemical techniques to date bones andartifacts and identify their origins Although law is not normally considered a fieldrelated to chemistry, forensic scientists use chemical methods to analyze blood,fibers, and other evidence as they investigate crimes In particular, DNA

matching—comparing biological samples of genetic material to see whether theycould have come from the same person—has been used to solve many high-profilecriminal cases as well as clear innocent people who have been wrongly accused orconvicted Forensics is a rapidly growing area of applied chemistry In addition, theproliferation of chemical and biochemical innovations in industry is producingrapid growth in the area of patent law Ultimately, the dispersal of information inall the fields in which chemistry plays a part requires experts who are able toexplain complex chemical issues to the public through television, print journalism,the Internet, and popular books

Figure 1.1 Chemistry in Everyday Life

Although most people do not recognize it, chemistry and chemical compounds are crucial ingredients in almost everything we eat, wear, and use.

By this point, it shouldn’t surprise you to learn that chemistry was essential inexplaining a pivotal event in the history of Earth: the disappearance of thedinosaurs Although dinosaurs ruled Earth for more than 150 million years, fossilevidence suggests that they became extinct rather abruptly approximately 66million years ago Proposed explanations for their extinction have ranged from anepidemic caused by some deadly microbe or virus to more gradual phenomena such

as massive climate changes In 1978 Luis Alvarez (a Nobel Prize–winning physicist),the geologist Walter Alvarez (Luis’s son), and their coworkers discovered a thinlayer of sedimentary rock formed 66 million years ago that contained unusuallyhigh concentrations of iridium, a rather rare metal (part (a) inFigure 1.2 "Evidencefor the Asteroid Impact That May Have Caused the Extinction of the Dinosaurs").This layer was deposited at about the time dinosaurs disappeared from the fossilrecord Although iridium is very rare in most rocks, accounting for only 0.0000001%

of Earth’s crust, it is much more abundant in comets and asteroids Becausecorresponding samples of rocks at sites in Italy and Denmark contained highiridium concentrations, the Alvarezes suggested that the impact of a large asteroidwith Earth led to the extinction of the dinosaurs When chemists analyzed

additional samples of 66-million-year-old sediments from sites around the world, allwere found to contain high levels of iridium In addition, small grains of quartz inmost of the iridium-containing layers exhibit microscopic cracks characteristic ofhigh-intensity shock waves (part (b) inFigure 1.2 "Evidence for the Asteroid ImpactThat May Have Caused the Extinction of the Dinosaurs") These grains apparentlyoriginated from terrestrial rocks at the impact site, which were pulverized onimpact and blasted into the upper atmosphere before they settled out all over theworld

Figure 1.2 Evidence for the Asteroid Impact That May Have Caused the Extinction

of the Dinosaurs

(a) Luis and Walter Alvarez are standing in front of a rock formation in Italy that shows the thin white layer of iridium-rich clay deposited at the time the dinosaurs became extinct The concentration of iridium is 30 times higher in this layer than in the rocks immediately above and below it There are no significant differences between the clay layer and the surrounding rocks

in the concentrations of any of the 28 other elements examined (b) Microphotographs of an unshocked quartz grain (left) and

a quartz grain from the rich layer exhibiting microscopic cracks resulting from shock (right).

iridium-Scientists calculate that a collision of Earth with a stonyasteroid about 10 kilometers (6 miles) in diameter,traveling at 25 kilometers per second (about 56,000miles per hour), would almost instantaneously releaseenergy equivalent to the explosion of about 100 millionmegatons of TNT (trinitrotoluene) This is more energythan that stored in the entire nuclear arsenal of theworld The energy released by such an impact would setfire to vast areas of forest, and the smoke from the firesand the dust created by the impact would block thesunlight for months or years, eventually killing virtuallyall green plants and most organisms that depend on

them This could explain why about 70% of all

species—not just dinosaurs—disappeared at the sametime Scientists also calculate that this impact wouldform a crater at least 125 kilometers (78 miles) indiameter Recently, satellite images from a SpaceShuttle mission confirmed that a huge asteroid or cometcrashed into Earth’s surface across the Yucatan’s

northern tip in the Gulf of Mexico 65 million years ago,leaving a partially submerged crater 180 kilometers (112miles) in diameter (Figure 1.3 "Asteroid Impact") Thussimple chemical measurements of the abundance of oneelement in rocks led to a new and dramatic explanationfor the extinction of the dinosaurs Though still

controversial, this explanation is supported byadditional evidence, much of it chemical

Figure 1.3 Asteroid Impact

The location of the asteroid impact crater near what is now the tip of the Yucatan Peninsula in Mexico.

This is only one example of how chemistry has been applied to an importantscientific problem Other chemical applications and explanations that we willdiscuss in this text include how astronomers determine the distance of galaxies andhow fish can survive in subfreezing water under polar ice sheets We will alsoconsider ways in which chemistry affects our daily lives: the addition of iodine totable salt; the development of more effective drugs to treat diseases such as cancer,AIDS (acquired immunodeficiency syndrome), and arthritis; the retooling of

industry to use nonchlorine-containing refrigerants, propellants, and otherchemicals to preserve Earth’s ozone layer; the use of modern materials inengineering; current efforts to control the problems of acid rain and globalwarming; and the awareness that our bodies require small amounts of somechemical substances that are toxic when ingested in larger doses By the time youfinish this text, you will be able to discuss these kinds of topics knowledgeably,either as a beginning scientist who intends to spend your career studying suchproblems or as an informed observer who is able to participate in public debatesthat will certainly arise as society grapples with scientific issues

Chemistry is the study of matter and the changes material substances undergo.

It is essential for understanding much of the natural world and central to manyother scientific disciplines, including astronomy, geology, paleontology,

biology, and medicine

K E Y T A K E A W A Y

• An understanding of chemistry is essential for understanding much ofthe natural world and is central to many other disciplines

1.2 The Scientific Method

L E A R N I N G O B J E C T I V E

1 To identify the components of the scientific method

Scientists search for answers to questions and solutions to problems by using aprocedure called thescientific method3 This procedure consists of making

observations, formulating hypotheses, and designing experiments, which in turn lead to

additional observations, hypotheses, and experiments in repeated cycles (Figure 1.4

"The Scientific Method")

Figure 1.4 The Scientific Method

As depicted in this flowchart, the scientific method consists of making observations, formulating hypotheses, and designing experiments A scientist may enter the cycle at any point.

3 The procedure that scientists

use to search for answers to

questions and solutions to

problems.

Observations can be qualitative or quantitative Qualitative observations describe

properties or occurrences in ways that do not rely on numbers Examples ofqualitative observations include the following: the outside air temperature is coolerduring the winter season, table salt is a crystalline solid, sulfur crystals are yellow,and dissolving a penny in dilute nitric acid forms a blue solution and a brown gas

Quantitative observations are measurements, which by definition consist of both a number and a unit Examples of quantitative observations include the following: the

melting point of crystalline sulfur is 115.21 degrees Celsius, and 35.9 grams of tablesalt—whose chemical name is sodium chloride—dissolve in 100 grams of water at 20degrees Celsius For the question of the dinosaurs’ extinction, the initial

observation was quantitative: iridium concentrations in sediments dating to 66million years ago were 20–160 times higher than normal

After deciding to learn more about an observation or a set of observations,scientists generally begin an investigation by forming ahypothesis4, a tentativeexplanation for the observation(s) The hypothesis may not be correct, but it putsthe scientist’s understanding of the system being studied into a form that can betested For example, the observation that we experience alternating periods of lightand darkness corresponding to observed movements of the sun, moon, clouds, andshadows is consistent with either of two hypotheses: (1) Earth rotates on its axisevery 24 hours, alternately exposing one side to the sun, or (2) the sun revolvesaround Earth every 24 hours Suitable experiments can be designed to choosebetween these two alternatives For the disappearance of the dinosaurs, thehypothesis was that the impact of a large extraterrestrial object caused theirextinction Unfortunately (or perhaps fortunately), this hypothesis does not lenditself to direct testing by any obvious experiment, but scientists can collectadditional data that either support or refute it

After a hypothesis has been formed, scientists conduct experiments to test itsvalidity.Experiments5are systematic observations or measurements, preferably

made under controlled conditions—that is, under conditions in which a single

variable changes For example, in our extinction scenario, iridium concentrationswere measured worldwide and compared A properly designed and executedexperiment enables a scientist to determine whether the original hypothesis isvalid Experiments often demonstrate that the hypothesis is incorrect or that itmust be modified More experimental data are then collected and analyzed, atwhich point a scientist may begin to think that the results are sufficientlyreproducible (i.e., dependable) to merit being summarized in alaw6, a verbal ormathematical description of a phenomenon that allows for general predictions A

law simply says what happens; it does not address the question of why One example

of a law, thelaw of definite proportions7, which was discovered by the Frenchscientist Joseph Proust (1754–1826), states that a chemical substance alwayscontains the same proportions of elements by mass Thus sodium chloride (table

4 A tentative explanation for

scientific observations that

puts the system being studied

into a form that can be tested.

5 A systematic observation or

measurement, preferably made

under controlled

conditions—that is, conditions

in which the variable of

interest is clearly distinguished

from any others.

6 A verbal or mathematical

description of a phenomenon

that allows for general

predictions and says what

happens, not why it happens.

7 A chemical substance always

contains the same proportions

of elements by mass.

salt) always contains the same proportion by mass of sodium to chlorine, in thiscase 39.34% sodium and 60.66% chlorine by mass, and sucrose (table sugar) is always42.11% carbon, 6.48% hydrogen, and 51.41% oxygen by mass.You will learn inChapter 12 "Solids"that some solid compounds do not strictly obey the law ofdefinite proportions (For a review of common units of measurement, see EssentialSkills 1 inSection 1.9 "Essential Skills 1".) The law of definite proportions shouldseem obvious—we would expect the composition of sodium chloride to beconsistent—but the head of the US Patent Office did not accept it as a fact until theearly 20th century.

Whereas a law states only what happens, atheory8attempts to explain why nature

behaves as it does Laws are unlikely to change greatly over time unless a majorexperimental error is discovered In contrast, a theory, by definition, is incompleteand imperfect, evolving with time to explain new facts as they are discovered Thetheory developed to explain the extinction of the dinosaurs, for example, is thatEarth occasionally encounters small- to medium-sized asteroids, and theseencounters may have unfortunate implications for the continued existence of mostspecies This theory is by no means proven, but it is consistent with the bulk ofevidence amassed to date.Figure 1.5 "A Summary of How the Scientific Method WasUsed in Developing the Asteroid Impact Theory to Explain the Disappearance of theDinosaurs from Earth"summarizes the application of the scientific method in thiscase

8 A statement that attempts to

explain why nature behaves the

way it does.

Figure 1.5 A Summary of How the Scientific Method Was Used in Developing the Asteroid Impact Theory to Explain the Disappearance of the Dinosaurs from Earth

E X A M P L E 1

Classify each statement as a law, a theory, an experiment, a hypothesis, aqualitative observation, or a quantitative observation

a Ice always floats on liquid water

b Birds evolved from dinosaurs

c Hot air is less dense than cold air, probably because the components ofhot air are moving more rapidly

d When 10 g of ice were added to 100 mL of water at 25°C, the temperature

of the water decreased to 15.5°C after the ice melted

e The ingredients of Ivory soap were analyzed to see whether it really is99.44% pure, as advertised

Given: components of the scientific method Asked for: statement classification

b This is a possible explanation for the origin of birds, so it is a hypothesis

c This is a statement that tries to explain the relationship between thetemperature and the density of air based on fundamental principles, so

a Measured amounts of acid were added to a Rolaids tablet to see whether

it really “consumes 47 times its weight in excess stomach acid.”

b Heat always flows from hot objects to cooler ones, not in the oppositedirection

c The universe was formed by a massive explosion that propelled matterinto a vacuum

d Michael Jordan is the greatest pure shooter ever to play professionalbasketball

e Limestone is relatively insoluble in water but dissolves readily in diluteacid with the evolution of a gas

f Gas mixtures that contain more than 4% hydrogen in air are potentiallyexplosive

Because scientists can enter the cycle shown inFigure 1.4 "The Scientific Method"

at any point, the actual application of the scientific method to different topics cantake many different forms For example, a scientist may start with a hypothesisformed by reading about work done by others in the field, rather than by makingdirect observations

It is important to remember that scientists have a tendency to formulatehypotheses in familiar terms simply because it is difficult to propose somethingthat has never been encountered or imagined before As a result, scientistssometimes discount or overlook unexpected findings that disagree with the basicassumptions behind the hypothesis or theory being tested Fortunately, trulyimportant findings are immediately subject to independent verification byscientists in other laboratories, so science is a self-correcting discipline When theAlvarezes originally suggested that an extraterrestrial impact caused the extinction

of the dinosaurs, the response was almost universal skepticism and scorn In only 20years, however, the persuasive nature of the evidence overcame the skepticism ofmany scientists, and their initial hypothesis has now evolved into a theory that hasrevolutionized paleontology and geology

InSection 1.3 "A Description of Matter", we begin our discussion of chemistry with

a description of matter This discussion is followed by a summary of some of the

pioneering discoveries that led to our present understanding of the structure of the

fundamental unit of chemistry: the atom.

Summary

Chemists expand their knowledge by making observations, carrying out

experiments, and testing hypotheses to develop laws to summarize their

results and theories to explain them In doing so, they are using the scientific

method.

K E Y T A K E A W A Y

• Chemists expand their knowledge with the scientific method

C O N C E P T U A L P R O B L E M S

1 What are the three components of the scientific method? Is it necessary for anindividual to conduct experiments to follow the scientific method?

2 Identify each statement as a theory or a law and explain your reasoning

a The ratio of elements in a pure substance is constant

b An object appears black because it absorbs all the visible light that strikesit

c Energy is neither created nor destroyed

d Metals conduct electricity because their electrons are not tightly bound to

a particular nucleus and are therefore free to migrate

3 Identify each statement as a theory or a law and explain your reasoning

a A pure chemical substance contains the same proportion of elements bymass

b The universe is expanding

c Oppositely charged particles attract each other

d Life exists on other planets

4 Classify each statement as a qualitative observation or a quantitativeobservation

a Mercury and bromine are the only elements that are liquids at roomtemperature

b An element is both malleable and ductile

c The density of iron is 7.87 g/cm3

d Lead absorbs sound very effectively

e A meteorite contains 20% nickel by mass

5 Classify each statement as a quantitative observation or a qualitativeobservation

a Nickel deficiency in rats is associated with retarded growth

b Boron is a good conductor of electricity at high temperatures

c There are 1.4–2.3 g of zinc in an average 70 kg adult

d Certain osmium compounds found in air in concentrations as low as 10.7µg/m3 can cause lung cancer

Themass10of an object is the quantity of matter it contains Do not confuse anobject’s mass with itsweight11, which is a force caused by the gravitationalattraction that operates on the object Mass is a fundamental property of an objectthat does not depend on its location.In physical terms, the mass of an object isdirectly proportional to the force required to change its speed or direction A moredetailed discussion of the differences between weight and mass and the units used

to measure them is included in Essential Skills 1 (Section 1.9 "Essential Skills 1").Weight, on the other hand, depends on the location of an object An astronautwhose mass is 95 kg weighs about 210 lb on Earth but only about 35 lb on the moonbecause the gravitational force he or she experiences on the moon is approximatelyone-sixth the force experienced on Earth For practical purposes, weight and massare often used interchangeably in laboratories Because the force of gravity isconsidered to be the same everywhere on Earth’s surface, 2.2 lb (a weight) equals1.0 kg (a mass), regardless of the location of the laboratory on Earth

Under normal conditions, there are three distinct states of matter: solids, liquids, and

gases (Figure 1.6 "The Three States of Matter").Solids12are relatively rigid andhave fixed shapes and volumes A rock, for example, is a solid In contrast,liquids13

have fixed volumes but flow to assume the shape of their containers, such as abeverage in a can.Gases14, such as air in an automobile tire, have neither fixedshapes nor fixed volumes and expand to completely fill their containers Whereasthe volume of gases strongly depends on their temperature andpressure15(theamount of force exerted on a given area), the volumes of liquids and solids arevirtually independent of temperature and pressure Matter can often change fromone physical state to another in a process called aphysical change16 For example,liquid water can be heated to form a gas called steam, or steam can be cooled to

9 Anything that occupies space

and has mass.

10 A fundamental property that

does not depend on an object’s

location; it is the quantity of

matter an object contains.

11 A force caused by the

gravitational attraction that

operates on an object The

weight of an object depends on

its location (c.f mass).

12 One of three distinct states of

matter that, under normal

conditions, is relatively rigid

and has a fixed volume.

13 One of three distinct states of

matter that, under normal

conditons, has a fixed volume

but flows to assume the shape

of its container.

14 One of three distinct states of

matter that, under normal

conditions, has neither a fixed

shape nor a fixed volume and

expands to completely fill its

container.

15 The amount of force exerted on

a given area.

16 A change of state that does not

affect the chemical

composition of a substance.

form liquid water However, such changes of state do not affect the chemicalcomposition of the substance.

Figure 1.6 The Three States of Matter

Solids have a defined shape and volume Liquids have a fixed volume but flow to assume the shape of their containers Gases completely fill their containers, regardless of volume.

Pure Substances and Mixtures

A pure chemical substance is any matter that has a fixed chemical composition and

characteristic properties Oxygen, for example, is a pure chemical substance that is

a colorless, odorless gas at 25°C Very few samples of matter consist of puresubstances; instead, most aremixtures17, which are combinations of two or morepure substances in variable proportions in which the individual substances retaintheir identity Air, tap water, milk, blue cheese, bread, and dirt are all mixtures Ifall portions of a material are in the same state, have no visible boundaries, and areuniform throughout, then the material ishomogeneous18 Examples of

homogeneous mixtures are the air we breathe and the tap water we drink

Homogeneous mixtures are also called solutions Thus air is a solution of nitrogen,

oxygen, water vapor, carbon dioxide, and several other gases; tap water is asolution of small amounts of several substances in water The specific compositions

17 A combination of two or more

pure substances in variable

proportions in which the

individual substances retain

their respective identities.

18 A mixture in which all portions

of a material are in the same

state, have no visible

boundaries, and are uniform

throughout.

Figure 1.7 A Heterogeneous Mixture

Under a microscope, whole milk

is actually a heterogeneous mixture composed of globules of fat and protein dispersed in water.

of both of these solutions are not fixed, however, but depend on both source and

location; for example, the composition of tap water in Boise, Idaho, is not the same

as the composition of tap water in Buffalo, New York Although most solutions weencounter are liquid, solutions can also be solid The gray substance still used bysome dentists to fill tooth cavities is a complex solid solution that contains 50%mercury and 50% of a powder that contains mostly silver, tin, and copper, withsmall amounts of zinc and mercury Solid solutions of two or more metals are

commonly called alloys.

If the composition of a material is not completely uniform, then it is

heterogeneous19(e.g., chocolate chip cookie dough, blue cheese, and dirt)

Mixtures that appear to be homogeneous are often found to be heterogeneous aftermicroscopic examination Milk, for example, appears to be homogeneous, but whenexamined under a microscope, it clearly consists of tiny globules of fat and proteindispersed in water (Figure 1.7 "A Heterogeneous Mixture") The components ofheterogeneous mixtures can usually be separated by simple means Solid-liquid

mixtures such as sand in water or tea leaves in tea are readily separated by filtration,

which consists of passing the mixture through a barrier, such as a strainer, withholes or pores that are smaller than the solid particles In principle, mixtures of two

or more solids, such as sugar and salt, can be separated by microscopic inspectionand sorting More complex operations are usually necessary, though, such as whenseparating gold nuggets from river gravel by panning First solid material is filteredfrom river water; then the solids are separated by inspection If gold is embedded inrock, it may have to be isolated using chemical methods

Homogeneous mixtures (solutions) can be separatedinto their component substances by physical processesthat rely on differences in some physical property, such

as differences in their boiling points Two of theseseparation methods are distillation and crystallization

Distillation20makes use of differences in volatility, a

measure of how easily a substance is converted to a gas

at a given temperature.Figure 1.8 "The Distillation of aSolution of Table Salt in Water"shows a simple

distillation apparatus for separating a mixture ofsubstances, at least one of which is a liquid The mostvolatile component boils first and is condensed back to aliquid in the water-cooled condenser, from which itflows into the receiving flask If a solution of salt andwater is distilled, for example, the more volatilecomponent, pure water, collects in the receiving flask,while the salt remains in the distillation flask

19 A mixture in which a material

is not completely uniform

Distillation makes use of

differences in the volatilities of

the component substances.

Figure 1.8 The Distillation of a Solution of Table Salt in Water

The solution of salt in water is heated in the distilling flask until it boils The resulting vapor is enriched in the more volatile component (water), which condenses to a liquid in the cold condenser and is then collected in the receiving flask.

Mixtures of two or more liquids with different boiling points can be separated with

a more complex distillation apparatus One example is the refining of crudepetroleum into a range of useful products: aviation fuel, gasoline, kerosene, dieselfuel, and lubricating oil (in the approximate order of decreasing volatility) Anotherexample is the distillation of alcoholic spirits such as brandy or whiskey Thisrelatively simple procedure caused more than a few headaches for federalauthorities in the 1920s during the era of Prohibition, when illegal stills proliferated

in remote regions of the United States

Crystallization21separates mixtures based on differences in solubility, a measure of

how much solid substance remains dissolved in a given amount of a specified liquid.Most substances are more soluble at higher temperatures, so a mixture of two ormore substances can be dissolved at an elevated temperature and then allowed to

cool slowly Alternatively, the liquid, called the solvent, may be allowed to

evaporate In either case, the least soluble of the dissolved substances, the one that

is least likely to remain in solution, usually forms crystals first, and these crystals

21 A physical process used to

can be removed from the remaining solution by filtration.Figure 1.9 "TheCrystallization of Sodium Acetate from a Concentrated Solution of Sodium Acetate

in Water"dramatically illustrates the process of crystallization

Figure 1.9 The Crystallization of Sodium Acetate from a Concentrated Solution of Sodium Acetate in Water

The addition of a small “seed” crystal (a) causes the compound to form white crystals, which grow and eventually occupy most of the flask (b).

Most mixtures can be separated into pure substances, which may be eitherelements or compounds Anelement22, such as gray, metallic sodium, is a substancethat cannot be broken down into simpler ones by chemical changes; acompound23,such as white, crystalline sodium chloride, contains two or more elements and haschemical and physical properties that are usually different from those of theelements of which it is composed With only a few exceptions, a particularcompound has the same elemental composition (the same elements in the sameproportions) regardless of its source or history The chemical composition of asubstance is altered in a process called achemical change24 The conversion of two

or more elements, such as sodium and chlorine, to a chemical compound, sodiumchloride, is an example of a chemical change, often called a chemical reaction.Currently, about 115 elements are known, but millions of chemical compounds have

22 A pure substance that cannot

be broken down into a simpler

substance by chemical changes.

23 A pure substance that contains

two or more elements and has

chemical and physical

properties that are usually

different from those of the

elements of which it is

composed.

24 A process in which the

chemical composition of one or

more substances is altered.