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Lecture Notes for Chemistry: The Science in Context, 3rd Edition

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    Chemistry: The Science in Context Third Edition INSTRUCTOR’S RESOURCE MANUAL with ChemConnections Activities

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    Chemistry: The Science in Context Third Edition Thomas R. Gilbert, Rein V. Kirss, Natalie Foster, Geoffrey Davies Rein V. Kirss nor T h E a STE rn univ E r S i T y with contributing authors Sharon Anthony Tricia Ferrett Sandra Laursen George Lisensky Heather Mernitz W • W • NORTON & COMPANY • NEW YORK • LONDON INSTRUCTOR’S RESOURCE MANUAL with ChemConnections Activities

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    Preface vi Chapter 1 | Matter, Energy, and the Origins of the Universe 1 Chapter 2 | Atoms, Ions, and Compounds 6 Chapter 3 | Chemical Reactions and Earth’s Composition 11 Chapter 4 | Solution Chemistry and the Hydrosphere 18 Chapter 5 | Thermochemistry 23 Chapter 6 | Properties of Gases: The Air We Breathe 34 Chapter 7 | Electrons in Atoms and Periodic Properties 43 Chapter 8 | Chemical Bonding and Climate Change 55 Chapter 9 | Molecular Geometry and Bonding Theories 65 Chapter 10 | Forces between Ions and Molecules 75 Chapter 11 | Solutions and Their Colligative Properties 84 Chapter 12 | The Chemistry of Solids 88 Chapter 13 | Organic Chemistry: Fuels, Pharmaceuticals, and Materials 95 Chapter 14 | Thermodynamics: Spontaneous Processes, Entropy, and Free Energy 103 Chapter 15 | Chemical Kinetics 107 Chapter 16 | Chemical Equilibrium 122 Chapter 17 | Equilibrium in the Aqueous Phase 131 Chapter 18 | The Colorful Chemistry of Metals 139 Chapter 19 | Electrochemistry and the Quest for Clean Energy 144 Chapter 20 | Biochemistry: The Compounds of Life 152 Chapter 21 | Nuclear Chemistry 157 Chapter 22 | Life and the Periodic Table 164 ChemConnections Activity Worksheets 167 CONTENTS v

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    We set out to write Chemistry: The Science in Context, Third Edition because we believe that too many students view general chemistry courses as collections of chemi- cal facts and algorithms to be memorized—a belief that is reinforced by the current generation of texts. Missing from them are the dynamism of scientific discovery and the connections between chemistry and the other sciences. When connections are addressed they are usually relegated to separate chapters that most faculty do not cover, or are briefly mentioned in boxes set off from the text, which are infrequently read by students. Chemistry: The Science in Context, Third Edition is a book in which interdisciplinary connections form a narra- tive that spans the chapters and frames the presentation of the chemistry. We took this approach because students only truly learn chemical principles when they construct their own meaning of them. Introducing chemical principles within discussions that draw from other sciences can pro- vide the desire to create meaning and the foundation from which to construct it. This manual offers suggestions for integrating the contextual material in the text and other con- textual themes into your lectures, and offers a rich trove of active-learning lecture resources. The sequence of chemical topics in Chemistry: The Science in Context, Third Edition will be familiar to anyone who has taught from a standard introductory chemistry textbook. f EATURES O f T h E instructor’s r esource manual Teaching the Context For each chapter, a concise Overview explains the rationale behind our selection of the chapter’s contextual framework. In it, we review the important chemical principles that are covered and offer practical advice for presenting the mate- rial in lecture. At times we may suggest a different order- ing of the topics than that in the text because—like a state function—the conversations you have with your students can take different paths to the same end. Teaching the Context shows how all of the concepts presented within a chapter fit the story as a whole. This section also highlights key terms and provides references to other chapters that you can use to signal the ways that a given chapter builds upon and anticipates material from other chapters. Sample Lecture Outlines highlight the familiar concep- tual framework upon which the contextual story hangs and offer a checklist of the concepts introduced in each chapter. In these outlines, each major heading takes the form of a question. This format mirrors the approach that we take in our own lectures and in our textbook; our goal is to help students assimilate knowledge in ways that will help them move away from excessive reliance on memorization and toward conceptual understanding. While we have chosen to link concepts to context in a way that allows us to construct an overall storyline within our textbook, there are many other contextual avenues that we might have pursued for any given chapter. In fact, the specific examples matter less than the act of making, and encouraging students to make, these connections in the first place. We also recognize that in lecture, some instructors will want to use contextual examples that are different from those in the text. Alternative Contexts sections offer sugges- tions for augmenting your own store of favorite examples. Many of these come from two books that we have found to be rich sources of applied examples: What Einstein Told His Cook (R. Wolke) and Naturally Dangerous (J. Collman). For each chapter, we have suggested at least one alternative contextual storyline. In some cases, the same context can be carried through several chapters. Creating a Dynamic, Student-Centered Learning Environment The Active and Collaborative Classroom Exercises section of the manual offers two unique lecture resources that fur- ther develop conceptual understanding and promote active learning: ChemTours and ChemConnections Activities. We have included clicker questions selected from Margaret R. Asirvatham, Clickers in Action (W. W. Norton) vi P RE f ACE

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    for use during lectures. This book includes several chapters on the philosophy and application of clicker questions. Clicker questions allow for rapid testing of student under- standing of concepts during a lecture. The full set of Clickers in Action questions, with chapter and question numbers revised to reflect the Chemistry table of contents, can be downloaded from wwnorton.com/instructors. The ChemTours are designed to reinforce conceptual understanding through carefully developed tutorials dem- onstrating dynamic processes that help students visualize concepts at the molecular level. In many cases, students can manipulate variables and observe the resulting changes to a system. Questions at the end of tutuorials guide students through step-by-step problem-solving exercises and offer useful feedback. Students have access to a scientific cal- culator and interactive periodic table within each tutorial. Key equations and definitions are just a few clicks away. ChemTours are freely available on the StudySpace student website and are also integrated within SmartWork. Offline versions are also available for use in lecture. Short descrip- tions of relevant ChemTours are presented in each chapter of this manual for quick reference. ChemConnections Activities, like the ChemConnections Modules from which they are derived, are intended to help students learn chemistry through active and collaborative engagement in real-world problems that require chemis- try knowledge and scientific thinking skills. Research has shown that students learn best when they are engaged in learning activities that: (1) build on past experience, (2) relate what they are learning to things that are relevant to them, (3) take part in “hands-on” experiences, (4) construct their own knowledge in collaboration with other students and faculty, and (5) communicate their results effectively. 1 Many faculty are interested in this student-centered pedagogical approach but have found that developing activities that work well, tell a coherent story, and cover the appropriate chemistry content is very time-demanding. That’s where the ChemConnections Modules and Activities come in. They cover a broad range of chemical topics and supply research-based, classroom-tested, active learning strategies that guide students through the scientific process. The activities in this manual include some of the authors’ favorite activities from a few of the modules. They are pro- vided here as resources for instructors who wish to try out more active methods of teaching and learning, as examples for instructors who wish to design their own activities, and as invitations for instructors intrigued with this style of pedagogy to investigate the full set of ChemConnections Modules. 1 How People Learn: Brain, Mind, Experience, and School. John D. Bransford, Ann L. Brown, and Rodney R. Cocking, editors. National Research Council: National Academy Press, Washington, DC, 1999. Because the activities have been adapted from the mod- ules, they have been classroom tested in a form very similar to what is provided here. This Instructor’s Resource Manual includes photocopy-ready worksheets for students with introductory text, instructions, questions, data, and space for notes and answers. The authors have also provided their best advice, as module authors and teachers, about how to guide students through these activities, and have pointed out places where you will need to make choices to adapt them to your own students and classroom settings. Many of the activities are collaborative, asking students to work in small groups to solve a problem or to make sense of data. Students benefit from group work by organizing their ideas, giving explanations, and listening to alternate or conflicting ideas. The activities also include opportunities for students to express their understanding individually. Some of the activities use pencil and paper while others are hands-on and may even be a little messy! When using any of the activities here, some general “good practices” should be kept in mind. Each activity should have a beginning, a middle, and an end. The instruc- tor may set the stage by explaining the goals of the activity and introducing its logistics. During the activity, circulate to listen to student discussions and keep students on task. Let them struggle with the ideas a bit, even when the tempta- tion is strong to jump in and offer assistance. Help students value the group process and recognize that, in group work, a thoughtful question or request for more explanation is often as valuable as the “right answer.” For the same reason, it is usually best not to collect the worksheets for grading; they are intended to prompt student thinking and serve as a work space to record ideas that are under construction. If you wish to assess student learning from the activity, choose one of the questions from the end of the worksheet that requires a summary or application of concepts, and have students prepare individual or group answers as a short in-class writ- ing assignment or as a homework problem. At the end of the activity, take a few minutes to review the goals of the activ- ity so that students feel confident they have understood the point, address any issues or questions that arose, and help students see how the ideas fit in with other topics recently studied. For more ideas on how to incorporate effective active learning into classrooms, see the ChemConnections Guide to Teaching with Modules . Media Resources Additional lecture support is offered from the Norton Instructor Resource Disc DVD-ROM and the online Norton Resource Library , which make available all the line art and tables from Chemistry: The Science in Context, Third Edition as JPEG images and PowerPoint slides, lec- ture outline slides, clicker questions in PowerPoint, and Preface | vii

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    PowerPoint-ready offline versions of the approximately 100 ChemTours from StudySpace. Clicker Questions from c lickers in a ction Each chapter contains suggested clicker questions that have been selected from Margaret R. Asirvatham, Clickers in Action (W. W. Norton). The questions were chosen to reflect the concepts introduced in the Sample Lecture Outline. The full set of Clickers in Action questions, with chapter and ques- tion numbers revised to directly reflect the Chemistry table of contents, can be downloaded from wwnorton.com/instructors. Suggestions for Lecture Demonstrations and Labs The Resources section that concludes each chapter provides extensive references to published classroom demonstrations, and offers suggestions for laboratory exercises. We recom- mend Chemical Education Resources (CER) laboratory exercises because we have used these experiments in our courses and find them to be clear and effective, with com- plete protocols, thoughtful pre- and post-lab questions, and well-designed report formats. Each experiment description comes with comprehensive instructor’s information. Conclusion The take-home message of this manual is that the degree to which you align your lectures and other learning activities to the contexts used in the text is completely up to you. All of us have our favorite stories and anecdotes with which to connect our students to the principals of chemistry. We encourage you to use yours. That way your students will have a variety of experiences linking their personal and professional interests to the world of chemistry. Multiple contexts also reinforce the message that chemistry truly is the central science. viii | Preface

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    1 CHAPTER 1 Matter, Energy, and the Origins of the Universe Ov ER vi E w The objective of the opening chapter is to make a case for the relevance of chemistry in our lives and to prospective careers. Following this introduction, matter and energy are defined, mixtures and their separation are discussed, and the scientific method is outlined. The remainder of the chapter focuses on measurement and unit conversions. Our approach introduces many of these topics using substances familiar to most students such as gold and water. For many students, the material in Chapter 1 is neither new nor particularly exciting. Some students are well versed in the topics in the chapter and may be bored by the repetition of this information. Others, however, are not as confident and need the foundation presented in Chapter 1. The challenge to an instructor is how to accommodate the needs of both groups. Our solution is to start by asking how the universe may have begun. Through an examination of selected observa- tions that support the Big Bang theory, we hope to catch the attention of students at all levels. For example, the residual thermal signal from the Big Bang leads to a review of tem- perature scales. We present further evidence in the form of the microwave afterglow of the Big Bang that was predicted in the 1940s and discovered by accident in the 1960s. We believe this contextual approach powerfully reinforces the central role of chemistry among the sciences. It also engages the students in an examination of the workings of the scien- tific method by using a topic with which many have some familiarity. A more detailed discussion of the Big Bang theory requires an introduction to the pioneering work of Edwin Hubble in the 1920s. Hubble’s discovery that galaxies out- side the Milky Way were receding supplied evidence to sup- port the Big Bang hypothesis. To address Hubble’s evidence for an expanding universe, we need to discuss redshifts and the Doppler effect. While these topics are not included in Chapter 1, you may wish to supplement the textbook on these topics. A discussion of redshifts requires an introduc- tion to the wave properties of radiation and to equations describing their behavior—for example, c = ln and E = h n . The fundamentals of the wave nature of light can be found in Chapter 7, section 7.1. To challenge your audience, you may wish to move that material forward to Chapter 1. For a more adventurous instructor, the simple relation between temperature and wavelength given off by an object heated to a very high temperature, l max = 2.897 × 10 6 nm ⋅ K/T, is key to understanding the microwave afterglow of the Big Bang and may prove stimulating to students who have studied measurements and unit conversions in middle and high school. We believe these discussions and those of the discovery of heterogeneities in the microwave background in the 1990s add an intriguing perspective on the dynamics of scientific discovery. With the Big Bang, we set the stage for constructing atoms from subatomic particles and work toward more- complex structures. Thus, we favor the bottom-up approach, starting with a microscopic view and building toward a macroscopic picture of matter. We hope to help students understand atomic structure before turning to the chemical properties of the elements and the formation of compounds. We recognize that you, the instructor, may have your own favorite contexts within which to frame your classroom discussion of the traditional topics in Chapter 1. We hope you will use them. Additional contexts will challenge your students to see the similarities between those in the book and those presented in class. For example, one member of the author team uses a can of carbonated beverage to intro- duce the concepts of mass, volume, and density, as well as the differences among the states of matter and among pure elements and heterogeneous and homogeneous mixtures.

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    2 | Chapter 1 This context is one that every student can identify and understand. Chapter 1 and those that follow it include three features that we hope prove useful to you and your students. Each Sample Exercise is solved and paired with an unsolved Practice Exercise. Concept Tests are intended to compel the reader to pause and provide a nonnumerical answer. As an instructor, you might use these questions as the basis for in- class discussion. Each Sample Exercise is solved using a set of steps: C ollect and O rganize, A nalyze, S olve, and T hink ( coast ) about it. coast is by no means the only effective problem-solving methodology. You may have a time-tested method of your own. However, for the novice student, coast provides one approach to problem solving. coast is consistently applied in the solutions to all of the Sample Exercises in this textbook and to the support package. TEACH ing THE CO n TE x T The opening chapter of a general chemistry textbook poses a challenge to a textbook author. Typically, the content is light on chemistry. Certain topics such as measurement and unit conversions are unlikely to evoke an enthusiastic response from students. One is often tempted just to skip this mate- rial altogether in favor of “real chemistry” in subsequent chapters. Nevertheless, given the diversity in background of the students, these topics must be included and discussed. What we have tried to do in Chapter 1 is to combine stan- dard introductory material with a more interesting story. Consistently throughout this book we start with obser- vations of the world around us. We see familiar objects around us, all of which are examples of matter (section 1.1). Chemistry is the science of matter. As an instructor, you might focus on some simple examples of matter in the classroom—some copper wire, a bottle of water a student may have brought to class, or a piece of gold jewelry. Of what are these examples of matter composed? Matter has mass (an extensive property ) and occupies space. All matter is composed of atoms (Figure 1.5). Copper wire is an example of a pure substance as well as an element , copper, which has certain physical properties such as density , an intensive property . Copper is malleable, duc- tile, and has high electrical conductivity. The tarnish on the wire is a chemical property of copper. One might even drop a little copper wire into nitric acid as a further demonstration of the chemical properties of copper, a chemical reaction that you can describe with a chemical equation . The text uses gold as an example of density determination (Figure 1.20). Is the gold jewelry you wear a pure substance? The answer is yes only if the gold is 24 karat. [One karat is equal to 1/24 (4.17%) of the weight of the metal in a mixture.] Drop a gold ring into nitric acid—nothing happens, showing the different chemical properties of copper and gold. You may need to cheat here and use a piece of cheap 14-karat gold jewelry rather than find some more expensive 22- or 24-karat gold. At this point it might be useful to reveal the periodic table of elements and locate copper, gold, and the other 110 elements. Which element is water? This may be a silly question to nearly everyone in the audience but is one that is worth ask- ing on the first day of class. A mixture of ice and water is a very useful visual aid or prop here. Water, of course, isn’t an element at all but a pure substance that is a compound with a chemical formula : H 2 O. Water is a molecule composed of the elements hydrogen and oxygen. Demonstrating that water is composed of two gaseous elements is easy if you have a simple electrolysis apparatus available. Connecting a large dry cell to two pencils immersed in a beaker of water is sufficient to illustrate the generation of hydrogen and oxy- gen. Water exists in three physical states: gas , liquid , and solid . Boiling the water on a hot plate illustrates the concept of water vapor. The choice of water, pre-1980 pennies, and 24-karat jewelry as examples has allowed you to cover the right-hand side of Figure 1.2, a standard illustration of the organization of matter. Why is it important to restrict our discussion to copper wire and 24-karat gold jewelry? Contemporary “copper” pennies are examples of heterogeneous mixtures : a zinc core surrounded by a copper cladding. A 14-karat earring is a homogeneous mixture of 58.3% Au and 41.7% Cu by mass. How would you separate the copper from the gold in 14-karat gold? Here is an opportunity to combine several observations. We have seen that nitric acid dissolves copper but not gold. Both metals and the homogeneous mixture of 14-karat gold (alloys are defined in Chapter 12) will dis- solve in a mixture of HCl and HNO 3 (aqua regia, 3:1). In principle, electrolysis (as for water) will deposit copper at a lower potential than that required for gold. The same proce- dure is applicable to the separation of copper from zinc in a penny. Both metals dissolve in nitric acid yet are deposited electrochemically at different potentials. It is tempting to demonstrate the etching of the copper from the outside of a penny with acid to show the zinc core. Distillation (Figure 1.12) of the homogeneous mixture obtained by dis- solving copper in nitric acid separates the water from the ionic compound copper nitrate based on volatility . If you restrict yourself to pennies and gold jewelry, then filtration becomes a bit trickier to illustrate. One choice is to evapo- rate the copper nitrate solution until crystals (solid) form, followed by filtration. This can be done during the lecture as part of the distillation demonstration. Copper wire and gold jewelry (assuming you did not sacrifice them to the acid treatment) provide the context for discussing measurement, conversion factors , the uncer- tainty inherent in all measurements, and the need to consider significant figures in both measurements and calculations involving experimental data (section 1.8). The density of either object can be calculated from measurements of the mass and volume (Figures 1.19 and 1.20). In making

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    Matter, Energy, and the Origins of the Universe | 3 each measurement, the uncertainty depends in part on the precision and accuracy of each measurement (Figure 1.22). The calculation of density forces you to take into account the number of significant figures dictated by your measurements. Where did matter come from? Unknowingly, perhaps, it is a question we have all probably asked on several occasions in our lives. The answer to this question may place you, the instructor, in a delicate position of address- ing the differences among hypotheses , theories , beliefs, and the role of the scientific method (sections 1.7 and 1.10 and Figure 1.18). We present the Big Bang as an example of a scientific hypothesis and evaluate some of the experimental evidence supporting this hypothesis as an illustration of the scientific method. For some students, coming to terms with the Big Bang hypothesis may prove problematic, so we have mentioned Hoyle’s skepticism in the same sentence as LeMaître’s hypothesis. Observations of receding galaxies are viewed as support for the Big Bang hypothesis but do not have to be presented with this emphasis. The residual thermal signal from the Big Bang provides an opportunity to review the three commonly used tempera- ture scales, Celsius , Fahrenheit , and Kelvin . S A m P l E lECT u RE Ou T lin E (Key Terms in Italics) What are copper wire and gold jewelry composed of? matter and atoms Figure 1.2 pure substance Figures 1.3 and 1.5 Clickers in Action , Chapter 1, Question 1 element physical properties chemical property Sample Exercise 1.1 intensive and extensive properties chemical reactions and chemical equations density Equation 1.1 Which element is water? compounds and molecules chemical formula physical states: gas, liquid, and solid Figures 1.14 and 1.15 Clickers in Action , Chapter 1, Question 6 Sample Exercise 1.2 electrolysis Figure 1.4 Is the gold jewelry you wear a pure substance? heterogeneous and homogeneous mixtures Figures 1.2 and 1.10 How would you separate the copper from the gold in 14-karat gold? distillation and filtration Figures 1.10 and 1.12 volatility Where did matter come from? hypotheses Figure 1.18 theories scientific method How do we know our jewelry is pure gold? units Tables 1.1–1.3 significant figures Figure 1.19 Sample Exercise 1.3 Figure 1.20 Sample Exercise 1.4 Clickers in Action , Chapter 1, Question 9 precision and accuracy unit conversions Figure 1.22 Sample Exercise 1.5 Sample Exercise 1.6 Sample Exercise 1.7 Should we believe in the Big Bang? Figure 1.29 Celsius, Fahrenheit, and Kelvin scales Figure 1.25 Equation 1.2 Equation 1.3 Sample Exercise 1.8 Clickers in Action , Chapter 1, Question 12 Al TER n ATivE C O n TE x TS (Key Terms Bolded) A Chemist’s v iew of a Soda Can We suspect that some instructors struggle with the question of how to make the study of chemistry seem relevant to a class of science majors from a variety of disciplines, of which chemistry majors are likely to be a minority or even absent. One answer is to provide the students with examples from the world around them. This is the basis for many of the science pages in magazines and newspapers as well as popular books written for the nonscientist. While we have chosen the Big Bang and origin of the universe as a medium to introduce the fundamentals of chemistry, there are many alternative contexts one could choose from that may be less controversial. One example is to focus on a can of soda such as Coke or Pepsi. Advertisements for these products abound, and there is a high probability that a student in your class has brought a can of soda to the lecture. You might want to bring one yourself. A can of soda contains examples of all three phases of matter: solid, liquid, and gas. The aluminum can (excluding the paint on the

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    4 | Chapter 1 outside) is a pure substance and an example of an element . Aluminum is a shiny ( lustrous ), malleable , ductile , and electrically conductive metal (or metalloid ), all of which are examples of physical properties . How can we use a can of Coca-Cola to illustrate chemical properties ? Ask the stu- dents to reflect on the fate of steel versus aluminum contain- ers left out in the rain by the side of the road. Iron rusts, but aluminum does not (ignoring for the moment that aluminum will slowly oxidize to aluminum oxide). The contents of the sealed can represent a homogeneous mixture containing the ingredients listed on the label. Once the can is opened, the unequal distribution of the gas bubbles makes it a heterogeneous mixture . The gas is carbon diox- ide, a molecular compound containing two nonmetallic elements, carbon and oxygen, with the molecular formula CO 2 . The sodium present in the soda is, of course, not in the elemental form but is found as the sodium cation with some unspecified anion to balance the charge. How could we separate this mixture? Distillation would allow us to remove the highly volatile CO 2 as well as to sepa- rate the water from the other ingredients based on volatility , leaving behind a mixture of molecular and ionic compounds. One could make the argument that as the volume of the solu- tion decreases, the precipitated solids can be removed by filtration . A can of soda typically is labeled with its volume, 12 fl oz or 355 mL. This represents a fine introduction to the units used in measurement and serves as an example of unit con- versions. Is 12 fl oz really 355 mL? Notice that the two val- ues contain different numbers of significant figures . How does this affect a calculation that converts 12 fl oz to mL? Notice that the mass of the soda is not given. How could we determine the mass of the solution (assuming that the mass of the can itself is minimal)? By weighing the can of soda we are forced to ask about the accuracy and precision of our measurement. Furthermore, with the mass of the soda in hand, we can calculate the density of the solution. Finally, most of us would prefer to drink our soda cold rather than warm. What do we mean by cold ? It clearly depends on which temperature scale we use: Fahrenheit , Celsius , or Kelvin . While 0°C might be a nice temperature for a “cold” soda, 0°F would probably leave us with a slush, and 0 K represents an unattainable, absolute zero . Throughout this Instructor’s Resource Manual we will return to the soda can as an example of an alternative context. A CT iv E A nd C O ll A b ORAT iv E Cl ASSROO m Ex ERC i SES Clickers in Action The following clicker questions have been selected from Margaret R. Asirvatham, Clickers in Action (W. W. Norton) and are available at wwnorton.com/instructors . The questions below were chosen to reflect the concepts introduced in the Sample Lecture Outline. The chapter and question numbers refer to PowerPoint slides from Clickers in Action. Clickers in Action , Chapter 1, Question 1 Which of these atomic and/or molecular views represent pure substances? A) I and III C) I, II, and IV B) II and IV D) II, III, and IV This question provides visual reinforcement of the differences among elements, compounds, pure substances, and mixtures. Clickers in Action , Chapter 1, Question 6 Dry ice sublimes at 25°C and 1 atmosphere pressure. Which equation is the correct symbolic representation for the change that occurs? A) CO 2 ( g ) → C( s ) + O 2 ( g ) C) CO 2 ( s ) → CO 2 (  ) B) CO 2 ( g ) → CO 2 ( s ) D) CO 2 ( s ) → CO 2 ( g ) We will return to phase changes at several points in the subsequent chapters; so the development of a clear distinction between melting, boiling, and sublimation is important. Students are also asked to look at chemical equations in this question. Clickers in Action , Chapter 1, Question 9 In which of these measured values are the zeros not significant figures? I) 0.0591 cm II) 504 g III) 2.70 m IV) 5300 L A) I and II D) I, III, and IV B) II and III E) II, III, and IV C) I and IV This question asks students to remember the rules of significant figures regarding zeros. This question could also be used to ask which number has the most significant figures or which ones have three significant figures. Clickers in Action , Chapter 1, Question 12 Neon has a boiling point of 27 K. Express this temperature in degrees Fahrenheit. A) 352°F C) –246°F B) 168°F D) – 411°F In general, clickers questions requiring calculations are more time consuming; however, students should be able to take an educated guess at the answer to this question. By I IV II III

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    Matter, Energy, and the Origins of the Universe | 5 limiting the time they have to answer the question, you can force them to practice estimation, or the “Analyze” step of the coast method for solving problems. ChemTours The following ChemTours are available on StudySpace (wwnorton.com/chemistry). Big Bang Section 1.7, p. 18 This animation explores the concept of the early formation of matter and radioactive decay rates within the context of the Big Bang. Significant Figures Section 1.8, p. 21 This ChemTour reviews the rules for assigning significant figures and walks students through sample calculations. It concludes with a series of interactive Practice Exercises that require students to express answers to addition, subtraction, multiplication, and division problems in significant figures. Scientific Notation Section 1.8, p. 21 This ChemTour explains how to use scientific notation to express very large and very small numbers, and how to eas- ily convert back and forth between decimal numbers and scientific notation. It includes Practice Exercises. Dimensional Analysis Section 1.9, p. 28 Students learn to keep track of the units associated with numerical values. The ChemTour includes worked examples and interactive Practice Exercises. Temperature Conversion Section 1.10, p. 30 Students practice converting between Fahrenheit, Celsius, and Kelvin temperature scales. The ChemTour includes Practice Exercises. R E f ERE n CES Classroom d emonstrations “Science Demonstrations, Experiments and Resources,” D. A. Katz, J. Chem. Educ. , 1991, 68, 235. “Ira Remsen’s Investigation of Nitric Acid,” in Chemical Demonstrations: A Sourcebook for Teachers , Vol. 2, L. R. Summerlin, C. L. Borgford, and J. B. Ealy, American Chemical Society, Washington, DC, 1988, p. 4. “The Mysterious Sunken Ice Cube,” in Chemical Demonstrations: A Sourcebook for Teachers , Vol. 2, L. R. Summerlin, C. L. Borgford, and J. B. Ealy, American Chemical Society, Washington, DC, 1988, p. 15. “Sugar in a Can of Soft Drink: A Density Exercise,” in Chemical Demonstrations: A Sourcebook for Teachers , Vol. 2, L. R. Summerlin, C. L. Borgford, and J. B. Ealy, American Chemical Society, Washington, DC, 1988, p. 126. “Densities and Miscibilities of Liquids and Liquid Mixtures,” D. A. Franz, J. Chem. Educ. , 1991, 68, 594. “Colorful Mixture Separation,” in Chemical Demonstrations: A Sourcebook for Teachers , Vol. 2, L. R. Summerlin, C. L. Borgford, and J. B. Ealy, American Chemical Society, Washington, DC, 1988, p. 17. “Separating Liquids: Fractional Distillation,” in Chemical Demonstrations: A Handbook for Teachers of Chemistry , Vol. 3, B. Z. Shakhashiri, University of Wisconsin Press, Madison, 1989, p. 258. “Meter Sticks in the Demonstration of Error Measurements,” R. Suder, J. Chem. Educ. , 1989, 66, 437. l aboratory Exercises We recommend the following Chemical Education Resources (CER) laboratory exercises for use with this chapter. We have used these experiments in our courses and find them to be clear and effective, with complete protocols, thoughtful pre- and post-lab questions, and well-designed report formats. Each experiment description comes with comprehensive instructor’s information. CER labs are published by Cengage Learning and are identified here by title and catalogue number. Order forms and additional information about the series are available from the CER website (www.CERlabs.com). CER: PROP 440, “Identifying a Liquid Using Physical Properties,” S. J. Melford and J. A. Anysas. Procedures to identify the physical properties of density, solubility in water and cyclohexane, and boiling point are followed using a known, then an unknown, liquid. The data are used to identify the unknown. CER: PROP 627, “Observing Some Physical and Chemical Changes in Matter,” G. W. Everett, G. W. Everett, Jr., and M. L. Gillette. Some physical and chemical properties of selected substances are observed. CER: PROP 393, “Studying Density Using Salad Oil and Vinegar,” Wendy Audrey Reichenbach. The densities of salad oil and vinegar are determined and compared. CER: PROP 495, “Classifying Matter by Properties,” Grover W. Everett and Grover W. Everett, Jr. The chemical and physical properties of selected substances are determined. The properties are used to separate mixtures of the substances. CER: MISC 521, “Using Statistics to Analyze Experimental Data,” Peter J. Krieger. The physical properties of some common objects are measured and the resulting data analyzed using statistics.

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    6 CHAPTER 2 Atoms, Ions, and Compounds OVERVIEW Chapter 2 begins with a relatively traditional discussion of the pioneering work of J. J. Thomson, Ernest Rutherford, and Robert A. Millikan but with an emphasis on how experimen- tal evidence led to the currently accepted model of an atom. The concept of the scientific method (Chapter 1) shows how the interpretation of data from critical experiments was essential to each scientist’s work. We are not unique in mentioning the contributions of F. W. Aston to the identification of isotopes; however, we feel it is also important to cite Aston’s work by name. Why is this important? Surely we are not suggesting that rote memorization of names is critical to understanding isotopic composition—it isn’t. The message we seek to convey is how Aston built on Thomson’s work and how it is related to Millikan’s and Rutherford’s contributions. At this point we examine some of the simple compounds in Earth’s crust and atmosphere. Discussing composition and chemical properties of matter creates the need to cover the conventions used to name compounds. We have chosen com- pounds found in the crust or present in the early atmosphere to illustrate the rules of nomenclature. Clearly, you could substitute your “favorite” compounds during classroom dis- cussions. You might take a consumer chemistry approach, as we have done with some of our illustrations. (A few of these products are also featured in Chapter 4.) Additional informa- tion on the chemistry of consumer products can be found in 1001 Chemicals in Everyday Products , 2nd ed., by Grace Ross Lewis (Wiley, 1999). Given a model of the atom, the shape of the periodic table begins to make sense, as we show students how elements in a group form ions with the same charge. (Electronic structure is not introduced until Chapter 7.) We end the chapter by addressing the process by which elements are made in stars: nucleosynthesis. This section closes the circle by explaining the statements in the final lines of Chapter 1, namely, how elements were created. Although we strongly urge you to teach the section on nucleosynthesis, section 2.9 may be used at your discretion. If the academic calendar dictates that it is time to move on to Chapter 3, failing to cover the story of nucleosynthesis will not harm students’ ability to comprehend the concepts in subsequent chapters. You can even return to section 2.9, if time allows you, when teaching nuclear chemistry (Chapter 21). TEACHING THE CONTEXT In our years of teaching general (introductory) college chemistry, we have observed that students are generally well versed in the overall structure of the atom. As early as middle school, they learn that atoms consist of a nucleus, which contains the protons (atomic number) and neutrons and which is surrounded by the electrons. The periodic table is based on atoms having different atomic numbers. Variability in the number of neutrons (forming isotopes) is discussed in secondary school chemistry classes. For an average student this foundation is quite solid. The names for compounds and ions, however, have probably faded from their short-term memory. These observations are relevant because these concepts constitute the bulk of Chapter 2. Why should an average student pay attention to lectures on atomic structure when he or she already knows it? This is the challenge to all instructors: how to make the material in this chapter new and relevant. Clearly, there are many approaches. We propose one solution: use the historical development of atomic structure to illustrate the application of the scientific method. By engaging students in how we know about atomic structure, as well as in what we know,

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    Atoms, Ions, and Compounds | 7 we challenge them on a different level from their prior expe- riences with chemistry. How and when did scientists first discern the commonly accepted picture of an atom? The notion of an atom as “plum pudding” (Figure 2.4) is just over 100 years old. Within five years of the publication of his model, J. J. Thomson’s concept of atoms as a sea of electrons dotted with protons had been replaced by Rutherford’s model of a nuclear atom surrounded by the electrons (Figure 2.7). Our current understanding of atomic structure developed in slightly more time than it will take the average student in your class to graduate from college. We believe that the notion of a five-year window of discovery will be more meaningful to a student than the knowledge that these dis- coveries were made between 1904 and 1909. One hundred years is way too long ago for all but a smattering of history buffs in your audience to appreciate. How did Rutherford disprove Thomson’s model? Starting from Thomson’s hypothesis and harnessing the work of Bequerel and the Curies, in addition to his own results on radioactivity, Rutherford and his students designed the experiment shown in Figure 2.6 that showed Thomson’s model to be in error. Rutherford did not work in a vacuum. He applied the scientific method to the problem by building on the work of other scientists in synthesizing a new explanation for a structure of the atom that was more consistent with the data. Among the other scientists whose work Rutherford needed was Thomson himself. Thomson had been the first to demonstrate the existence of electrons (cathode rays) as subatomic particles , and Millikan had established the charge on an electron that allowed the calculation of its mass. Studies of atomic structure did not end with Rutherford’s experiment; a significant amount of mass in atoms was still “missing”; the mass of the protons and electrons did not add up to the known atomic mass of the atom! Additional experimenta- tion by James Chadwick was needed to prove the existence of neutrons , while Francis Aston showed that atoms of the same element could exist as isotopes with the same atomic number but a different mass number . The natu- ral abundance of different isotopes underlies the concept of an average atomic mass for elements in the periodic table. All of this work spanned only a couple of decades, a fraction of a scientist’s working life. Your students may appreciate the time frame of these discoveries more than the actual dates when the experiments were conducted. Your class may find it interesting to know that Rutherford studied under Thomson while Aston and Chadwick were both Rutherford’s students! Carbon dioxide provides an example of the law of definite proportions, introduced in Chapter 1. Compounds such as SO 2 and SO 3 that contribute to acid precipitation make excellent examples of the law of multiple propor- tions . The introduction of nomenclature and chemical and molecular formulas for binary molecular compounds such as CO 2 , SO 2 , SO 3 , NO, and NO 2 held together by covalent bonds fits neatly into the discussion of atmospheric molecules. An example of binary ionic compounds is salt (Figure 2.6), composed of sodium cations and chloride anions . Students are all familiar with salt as a flavoring ingredient and in seawater. Consider the many possible compounds found in evaporated seawater besides sodium chloride. The alkali and alkaline earth metal halides (mostly chlorides) repre- sent the most prevalent compounds. Lower concentrations of ionic magnesium and calcium compounds are also pres- ent in such evaporites, including those with polyatomic ions and oxoanions (Tables 2.3 and 2.4). Earth’s crust is also rich in compounds of transition metals like iron and manganese, in which the metal cations often have a range of charges. The general shape of the periodic table has been known for some 140 years. Dimitri Mendeleev’s periodic table (Figure 2.10) was based on reactivity patterns of the known elements organized by groups and periods . Differences among the physical and chemical properties of metals , nonmetals , semimetals (metalloids) , and noble gases had been documented well before anyone had a clear idea of the structure of an atom. Where do the elements come from? While most students have seen the periodic table of the elements before entering college, few will be aware of nucleosynthesis , the forma- tion of the elements by nuclear processes in stars. Section 2.9 provides a nice answer to the question left unanswered at the end of Chapter 1: How did the Big Bang lead to different elements? At the end of Chapter 2, students are capable of understanding the basic nuclear reactions ( fusion , neutron capture , and β decay ) that account for synthesis of many elements in stars, including our sun. It is unlikely that many will have studied this in earlier courses, and we hope they will deepen their appreciation for the importance of atomic structure. After all, without the understanding of atomic structure developed by Rutherford and his peers early in the twentieth century, nuclear processes and the stellar nucleo- synthesis hypotheses could not have followed some 20 to 30 years later. For your students, accepting that the origins of all matter can be traced to the Big Bang should seem like a giant leap of faith. What evidence is there to support this hypothesis? Some of the evidence was presented in Chapter 1. Whether a student truly accepts the Big Bang hypothesis does not affect the observation that Earth is constructed from compounds of some 82 naturally occurring elements.

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    8 | Chapter 2 SAMPLE LECTURE OUTLINE (Key Terms in Italics) How do elements differ? What is the structure of an atom? plum pudding model (Dalton) Figure 2.4 cathode rays and electrons Figure 2.2 subatomic particles a particles b particles Rutherford–Geiger–Marsden experiment Figures 2.6 and 2.7 protons and neutrons Table 2.1 isotopes Figure 2.8 atomic number mass number Clickers in Action , Chapter 1, Question 4 Sample Exercise 2.1 natural abundance and average atomic mass Sample Exercise 2.2 What does the periodic table tell us? Mendeleev’s periodic table Figure 2.10 periods and groups metals, nonmetals, and metalloids Figure 2.11 noble gases Sample Exercise 2.3 Clickers in Action , Chapter 2, Question 13 What happens when we combine elements? law of multiple proportions Sample Exercise 2.4 binary molecular compounds Figure 2.15 molecular formula Table 2.2 Sample Exercise 2.5 Sample Exercise 2.6 binary ionic compounds Figure 2.16 Sample Exercise 2.7 Table 2.3 Clickers in Action , Chapter 2, Question 21 alkali metals alkali earth metals cations and anions Figure 2.17 empirical formula binary compounds of transition metals Sample Exercise 2.8 polyatomic ions and oxoanions Tables 2.3 and 2.4 Sample Exercise 2.9 Sample Exercise 2.10 Clickers in Action , Chapter 2, Question 17 acids Figure 2.19 Sample Exercise 2.11 Where did the elements come from? nucleosynthesis Figure 2.15 fusion of hydrogen Figures 2.16 and 2.17 Equations 2.2 and 2.3 neutron capture and b decay Figure 2.18 Equation 2.4 Sample Exercise 2.12 ALTERNATIVE CONTEXTS (Key Terms Bolded) A Chemist’s View of a Soda Can Revisited The readily identifiable can of soda you may have used as an alternative context in Chapter 1 works equally well in Chapter 2. The can is composed of aluminum, a metal or perhaps a metalloid . Carbon dioxide (CO 2 ) is a binary molecular compound (section 2.5) containing nonmetals held together by covalent bonds . Carbon dioxide remains a convenient starting point to introduce the law of defi- nite proportions, the law of multiple proportions (section 2.5), chemical formulas , and the nomenclature for binary molecular compounds (section 2.6). The presence of 50 mg of sodium cations in many sodas introduces nomenclature rules for alkali (and, by extension, alkaline earth ) metals . Clearly an anion must be present to balance the charge of the sodium ion. Two acids —phosphoric acid (H 3 PO 4 ) and carbonic acid (H 2 CO 3 )—are present in sufficient concen- tration to justify their inclusion on the list of ingredients. Both acids contain oxoanions , themselves examples of polyatomic ions (section 2.6). All of the elements found in many sodas can be located on the periodic table. As an element, aluminum can serve as a model for study- ing atomic structure. Aluminum atoms have nuclei containing protons (atomic number = 13) and neutrons , surrounded by 13 electrons. The structure of aluminum atoms can be inferred from Rutherford’s experiments. While aluminum is 100% natural abundance of 27 Al ( average mass = 26.98 amu), other isotopes exist. For example, 26 Al has a half-life of about 740,000 years and is seen in stars, where nucleosynthesis occurs. In the fall of 2007, it was reported that a new, very heavy isotope of aluminum ( 42 Al) had been detected. ACTIVE AND COLLABORATIVE CLASSROOM EXERCISES Clickers In Action The following clicker questions have been selected from Margaret R. Asirvatham, Clickers in Action (W. W. Norton) and are available on wwnorton.com/instructors . The questions below were chosen to reflect the concepts intro-

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    Atoms, Ions, and Compounds | 9 duced in the Sample Lecture Outline. The chapter and question numbers refer to PowerPoint slides from Clickers in Action. Clickers in Action, Chapter 2, Question 4 The ion 45 Sc 3+ has A) 24 electrons, 21 protons, and 24 neutrons B) 18 electrons, 21 protons, and 24 neutrons C) 24 electrons, 24 protons, and 21 neutrons D) 18 electrons, 24 protons, and 21 neutrons This question asks students to identify the number of protons, neutrons, and electrons in an ion. This question is more challenging than posing the same question for a neutral atom. Students will need to find Sc on the periodic table to determine the atomic number of Sc. You could modify the question by replacing, “ 45 Sc 3+ ” with “the 3+ ion of scandium-45.” In the latter case, students are also required to identify which element is scandium. Clickers in Action, Chapter 2, Question 13 Classify each statement about the periodic table as true (T) or false (F). Then, select the answer with the three correct letters (for example, TTT). I) In the modern periodic table, elements are arranged in order of increasing number of protons. II) Lead is a transition element. III) Radon is an inert gas. A) FTF C) FFT B) TFT D) TTF This question requires students to use the periodic table to identify the element symbols using the element name, to locate the element in the periodic table, and to assess whether each statement is true or false. Clickers in Action , Chapter 2, Question 17 Predict the correct name of the compound represented in the box. Nitrogen Oxygen A) Nitrogen oxide C) Dinitrogen monoxide B) Oxygen nitride D) Nitrogen dioxide This question addresses the molecular scale views of a chemical compound. Students must recognize the composition of the compound and then assign the correct name. Clickers in Action, Chapter 2, Question 21 Which compound is represented by the correct formula? Assume the names are correct. A) Magnesium phosphide: Mg 2 P 3 B) Magnesium phosphate: Mg 3 (PO 4 ) 2 C) Magnesium hydrogen phosphate: Mg(H 2 PO 4 ) 2 D) Magnesium dihydrogen phosphate: MgHPO 4 This question tests the students’ knowledge of nomenclature for inorganic salts containing polyatomic anions. Students may not have learned about “phosphide” but by analogy to “oxide,” they should be able to conclude that choice A is incorrect because the Mg ion carries a 2+ charge. ChemTours The following ChemTours are available on the StudySpace (wwnorton.com/chemistry). Cathode Ray Tube Section 2.1, p. 44 This ChemTour explores the effects of magnetic and electric fields and cathode rays. Millikan Oil Drop Experiment Section 2.1, p. 45 This ChemTour recreates the experimental procedure used by Millikan to determine the charge of an electron. Rutherford Experiment Section 2.1, p. 47 This recreates Rutherford’s gold foil experiment, which led to the discovery of the atomic nucleus. NaCl Reaction Section 2.5, p. 57 This ChemTour illustrates the process by which a metal and a nonmetal combine to form a binary ionic compound, as seen in the reaction of sodium metal and chlorine gas. Synthesis of Elements Section 2.7, p. 67 This ChemTour animates the neutron capture process and explains how elements are synthesized in stars. REFERENCES Classroom Demonstrations “An Easy Model for Teaching Mass/Charge in Mass Spectrometry,” R. V. F. Bravo and N. A. de Sousa, J. Chem. Educ. , 1989, 66, 1039. “General Chemistry Demonstrations Based on Nuclear and Radiochemical Phenomena,” R. H. Herber, J. Chem. Educ. , 1969, 46, 665.

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