Chemical Education Today edited by
Cheryl Baldwin Frech University of Central Oklahoma Edmond, OK 73034-5209
Introduction to Bonding and Hybridization Theory by William R. Sponholtz III Sponholtz Productions: Ashburnham, MA, 2008. DVDs. $29.00 (for each teacher version DVD); $19.00 (for each student version DVD). reviewed by Scott Smidt
Introduction to Bonding (run time 46 min) and Hybridization Theory (run time 34 min) are the products of William R. Sponholtz III and several students of Cushing Academy in Massachusetts. The DVDs teach the chemistry content visually and with accompanying narration. The videos feature chemical formulas, orbitals, and Lewis structures floating in front of natural landscapes and deep-space starscapes. Introduction to Bonding is divided into four segments (called chapters). The presentation begins with a series of questions, which should help students focus on the key points. The rest of the first chapter defines the different types of bonds and introduces electronegativity (and electronegativity differences) as a means to determine bond type. Students will need to understand electron configurations before watching this section. The next three chapters explain how to draw Lewis structures, beginning with individual atoms before moving on to compounds. The narration introduces several generalizations for drawing the structures (e.g., the octet rule), but also covers molecules that are considered “exceptions” to those generalizations. The narration does not explain why these exceptions exist, and this may be where the instructor can break away from the video to discuss the subject in more detail (if appropriate) or introduce formal charge as a guide for drawing Lewis structures (1). The DVD ends with examples drawn from simple organic compounds and includes discussions of isomerization and saturation of hydrocarbons. The second DVD, Hybridization Theory, consists of five chapters that introduce the subject; cover sp3, sp2, and sp hybridization; and summarize the material, with brief introductions to VSEPR theory and alternate conformations of organic molecules. Like Introduction to Bonding, this DVD begins with a series of questions to focus student attention. The ability to shift between 2-D and 3-D representations of molecules is emphasized throughout the presentation and should be very helpful to students. The narration covers not only the expected topics, such as sigma and pi bonds, but also Newman projections and cis-trans isomerism. The video does not tackle the terminology of molecular shapes (trigonal planar, bent, etc.) yet it does address how bond angles are altered by lone pairs of electrons. To fully appreciate the content presented, students will need prior exposure to electron configurations, Lewis structures, and atomic orbital shapes before viewing the DVD. Expectations of perfection will always be unsatisfied. So at the risk of overemphasizing minor flaws or focusing on pet peeves, here is my short list of things that detracted from the videos: Although the production values of both DVDs are 18
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generally quite good, I found the use of the color red for text and electrons made them sometimes difficult to see clearly against the landscapes of Introduction to Bonding. I might also quibble with the occasional anthropomorphizing of atoms and molecules when the narration refers to what atoms “want” or “desire”. We all do this, but should not; it diminishes the impact of the real explanation. I suppose this highlights the conundrum of how much simplification is too much. Finally, alert students might realize that in Chapter 1 of Introduction to Bonding they are told the noble gases do not have electronegativity values because they do not form bonds. Later, in Chapter 3, they are told that some noble gases can form bonds, and XeF4 is used as an example for drawing Lewis structures. I had never really thought about this before (the standard textbook figure showing electronegativities omits the noble gases), but is it true noble gases do not have electronegativity values, or simply that textbooks have redrawn the figure from Pauling's work, which predates the discovery of compounds with xenon? That spurred me to do some checking. Although Pauling did not change the figures or tables of electronegativity values in the 1970 edition of his basic chemistry textbook, he did estimate that the electronegativity of xenon was approximately 3.1 (2). And, of course, there are other methods for calculating electronegativities that assign values to some or all the noble gases. (For a general chemistry textbook that introduces an alternative measure of electronegativities, see ref 3.) It might be possible to use these parts of the video to highlight science as a process and how concepts are refined over time. These misdemeanors do not detract from the overall quality or usefulness of the videos, however. I plan to use these DVDs (particularly Hybridization Theory) in future classes, especially where the repeated shifting between two- and three-dimensional representations and the 360° rotations of molecules will help students immensely. These are things I cannot easily do myself, and the video demonstrates them exceptionally well. Although simply playing the DVDs in their entirety would be a fairly passive exercise, it should be possible to give students practice drawing Lewis structures or identifying the hybridization of atoms in a molecule by playing the beginning of a worked example on the DVD, then pausing the DVD while students work individually or in groups, then resuming the video so students can see the correct solution. I am sure that creative teachers of general chemistry and introductory organic chemistry will find additional applications. Another obvious use for the DVDs would be to put copies on reserve in a tutoring center or library for students to view if they need additional help on a topic. The videos can be ordered online (4), where sample clips of both DVDs are available along with review questions and answers. In addition, a third DVD, Understanding the Atom, has recently been produced and is available from the website also. The teacher and student versions are identical, but the teacher version comes with permission to show the DVD in public. It is also possible to purchase 90-day access to an online streaming version for $14.99.
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Chemical Education Today
Literature Cited 1. See, R. F. J. Chem. Educ. 2009, 86, 1241-1247; DOI: 10.1021/ ed086p1241. 2. Pauling, L. General Chemistry; Dover Publications: New York, 1988; p 251. 3. Spencer, J. N.; Bodner, G. M.; Rickard, L. H. Chemistry: Structure and Dynamics, 4th ed.; Wiley and Sons: New York, 2008; pp 134-135. 4. Sponholtz Productions Home Page. http://www.sponholtzproductions.com/ (accessed Oct 2010).
Scott Smidt teaches chemistry at Laramie County Community College, Albany County Campus, Laramie, WY 82070; ssmidt@ lccc.wy.edu. DOI: 10.1021/ed101004e Published on Web 11/03/2010
Physical Chemistry, 3rd Edition by Robert G. Mortimer Elsevier Academic Press: Burlington, MA, 2008. xvii þ 1396 pp. ISBN 978-0-12-370617-1 (paper). $65.00. reviewed by Francisco J. Rey Losada
Although many books have been published on physical chemistry, Mortimer's Physical Chemistry, 3rd edition, is a good example of a textbook that has adapted well to the changes in progress in chemical education. The book is divided into four main parts, which correspond with the classic sections of a general physical chemistry textbook: Chemical Thermodynamics; Dynamics (which includes transport processes and chemical kinetics); Quantum Chemistry (applied both to atoms and molecules); and last, with the evocative title of The Reconciliation of the Macroscopic and Molecular Theories of Matter, statistical thermodynamics and a brief study of the structure of the liquids and solids. Each of the parts is designed so that it can be studied independently, except the last one, which, in the author's words “is designed to be a capstone in which the other parts are integrated in a cohesive whole”. All chapters present a number of solved examples: 36 for the first law of the thermodynamics, 17 about chemical kinetics, 14 for heteronuclear diatomic molecules, and so on. The exercises have different degrees of difficulty, yet can be readily solved by any student who has understood the theory. Nevertheless, some more complex problems could be included to serve as a useful summary of each chapter's concepts. The book contains numerical solutions for a significant number of proposed problems; a solutions manual is also available, although students' use of this could undermine the effectiveness of working the problems in the text, so I advise against students obtaining the solutions manual. The presentation of the chapters in the Chemical Thermodynamics section follows a very intuitive, classic exposition. Students learn experimental facts and thermodynamic laws until r 2010 American Chemical Society and Division of Chemical Education, Inc.
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a point at which neither is well distinguished. The mathematical machinery then prevails, perhaps sometimes in an excessive way; however, unlike other texts, this book does not neglect the fundamental fact that thermodynamics is based on a wellestablished ensemble set of empirical facts. Thus, the first law directly flows from the (previous) concepts of heat and work, using ideal gases and chemical reactions as tools to fix the concepts with numerical applications. Other important thermodynamic functions such as entropy, or Gibbs and Hemholtz functions, are deduced from the second law (Carnot's theorem), which is thus applied to the previous systems. Meanwhile, students are prepared for more complex questions: phase equilibrium, solutions, chemical reactions, or equilibrium electrochemical systems. In my experience, many instructors prefer a different organization of the material. But, in any case, all the basic information is included in the text. I like the moderate treatment of pH and acidic systems because I believe it must be the students' responsibility to deepen their own understanding in these subject areas, if the instructor thinks that is necessary. The second main section is dedicated to dynamics and begins with the study of the kinetic-molecular theory of gases, which is quite important for two reasons. Fundamentally, it serves as an example of a deductive method to approach science. Kinetic-molecular theory of gases also provides a very simple model for the interpretation of the kinetic phenomena: the pressure of an ideal gas and the macroscopic laws of gases can be explained (from a microscopic point of view, of course), distribution plots can be made, and so forth. The study of transport in physical processes, basically in gases, but also with a brief discussion of the liquid systems and in electrolyte dissolutions, is then approached. Chemical kinetics is similarly explicated: a macroscopic mathematical description is used for different types of hypothetical reactions, and microscopic treatment, including the study of the reaction mechanisms, describes other types of systems, such as the oscillating catalysis or reactions about polymer formation. These topics are treated superficially; I found the amount of attention devoted to chemical kinetics (∼10% of the book) to be surprisingly low. The study of reaction mechanisms (including chain reactions) comprises only 40 pages, less than the author dedicates to thermodynamics of solutions. I believe that Chapter 12 (Chemical Reaction Mechanisms I) could be subdivided into two chapters, the first including theories about the rate of the reactions (molecular dynamics), and the other to less common yet important systems like the unimolecular gas reactions or solutions (theories of Lindemann and Smoluchowski). Other catalytic mechanisms and a more extensive description of photochemical processes could be included in Chapters 12 and 13. The second question related to this main section is its position in the text. As a professor, I have struggled with choosing when to introduce the variable time in the study of physical chemistry, mainly because many essential equations to do this come from other parts of physical chemistry. As mentioned above, the author thinks that each one of the chapters can be studied in an independent form. It is possible, but I believe that a better distribution of the topics would also require dividing this part into at least another two: one with Chapter 9, which must be explained before quantum chemistry (in fact, it would be better before the statistical mechanics); and another new part that
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would include physical transport and reaction rates after those two parts. The third main section of the text, the study of quantum chemistry and spectroscopy, occupies 11 of the 28 chapters of the book, which indicates the importance the author ascribes to these subjects. On the basis of the impossibility of classic mechanics to explain some experimental facts, quantum mechanics is constructed, and then applied to the simplest systems: the particle in a box and the quantum harmonic oscillator. Later the five postulates and their main applications are introduced (my experience guides me to change the order: first explain the five postulates and then apply them to the particle in a box, the harmonic oscillator, and the rigid rotor). The postulates are applied to more complex systems: hydrogen and hydrogen-like atoms, helium atom, polyelectronic atoms, and diatomic and polyatomic molecules, and, finally, to the analysis of the different types from spectroscopy. This third part is the best one in the text, with a level comparable, even superior, to those normally found in other general texts of physical chemistry, providing a good base for deeper studies. Of course, some will have different opinions on questions such as when the spin of the electron should be introduced first, but they are of much less significance than the questions of order mentioned above. The last section is dedicated to statistical mechanics, that is, the relation between the microscopic and the macroscopic worlds. Once again traditional methodology is used: the classic probability distribution is defined; molecular partition functions are inferred (studying these functions is necessary for a good explanation and understanding of the different types of spectroscopy); and molecular partition functions are then applied to equilibrium systems or liquid or polymeric solids. The placement of these subjects is not the most conducive; they could be better placed before quantum mechanics and, of course, before physical and chemical kinetics (an exception would be the gas kinetic theory). Thus, an arrangement ordered with thermodynamics first, followed by statistical mechanics, quantum mechanics, and then time-dependent systems would be more logical. I think students would better understand the logical and methodological development of physical chemistry with an order as I have just described. In any case, it is a matter of general discussion, and I believe that the users of the book will have the last word about the order of presentation of physical chemistry topics. Even though the quality of the book is excellent (paper, presentations, plots, figures, etc.), three issues of “aesthetics” must be mentioned. First, the weight of book (3.5 kg, 7.5 pounds in cloth version) is excessive; perhaps it could be published in two volumes, with thermodynamics and statistics in the first, and quantum mechanics and nonequilibrium in the second. On the other hand, approximately one-third of the pages' surface is not used, or it is used for anecdotal commentaries or figures that could be readily included in the text, for a better use of the space. Third, numerical errors, mainly in the thermodynamics equations, cause mathematical treatments that would have been trivial to become complicated. A technical revision would be beneficial. In summary, I strongly recommend this book both as a textbook for a general course on physical chemistry and as support for students studying physical chemistry whose instructors have decided not to use one discrete textbook. The few errors and questions about ordering topics do not detract from this 20
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fundamental fact: Physical Chemistry, 3rd edition is a very good text for the study of physical chemistry. Francisco J. Rey Losada teaches in the Department of Physical Chemistry, Universidade de Vigo, As Lagoas, Marcosende, 36310 Vigo Spain;
[email protected]. DOI: 10.1021/ed101028h Published on Web 11/01/2010
Physical Chemistry for the Biological Sciences, 1st ed. by Gordon G. Hammes John Wiley & Sons: Hoboken, New Jersey, 2007. 363 pp. ISBN 978-0470122020 (hardback). $87.78. reviewed by Michael P. McCann
Here at my institution, which is just down Interstate Highway 40 from that of the author, I have been considering whether or not I should go from a traditional “pchem” course to one more suitable for those majoring in biology and forensic science. I was quite interested, then, to see Gordon Hammes's book. He recognized quite some time ago the exciting research now being done in the area between physical chemistry and biochemistry. When I compared the size of Physical Chemistry for the Biological Sciences to those of Atkins (1), Noggle (2), or Berry, Rice and Ross (3), I wondered, would this be “Pchem for Dummies?” Many students of physical chemistry struggle with concepts such as wave functions, partition functions, entropy, and mathematics in general. Obviously, choices will have to be made about what topics to present students coming from a more biological background. Wave functions are discussed but only up to a particle in a one-dimensional box. There is no statistical mechanics other than a section on Statistical Effects of Ligand Binding in Macromolecules. Entropy is covered well from the classical thermodynamic viewpoint. There is a section titled Molecular Interpretation of Entropy, but it is only two paragraphs long and does not delve into statistical mechanics. Simple differential and integral equations are presented and solved. Knowledge of calculus would be helpful in following the text, although problems at the end of each chapter do not require the use of calculus. Partial derivatives are not employed. It seems I have focused on what the textbook does not have. In fact, while reading this book I often wondered whether I would have included a particular topic. In such a book, I would lean more toward no discussion of wave functions at all. So in some areas, the author is more thorough than I might be. Hammes focuses on areas more useful to biologists and biochemists, such as diffusion and kinetics. For example, the chapter titled Hydrodynamics of Macromolecules deals mainly with centrifugation. Having never read much about this, I found this quite interesting and obviously this material is quite useful to biologists and biochemists.
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The chapter Principles of Nuclear Magnetic Resonance and Electron Spin Resonance has a nice mixture of theory and examples from relatively recent research. For a book copyrighted in 2007, I found references to research as recent as 2003. I enjoyed reading about applications of physical chemistry to relatively modern biochemical research. Because the example on ESR research was over 30 years old, I believe that is something I would have left out. To me, another way to evaluate a textbook is to get into the nuts and bolts of problem solving. I wondered whether something had been omitted that would be needed to solve a problem at the end of a chapter. For the problems I examined, this was not an issue. The student problem solver has all the needed information in the chapter's text to solve the problem. Presumably the person using this book will already be somewhat familiar with biology and biochemistry. I believe that the examples of modern biochemical research will help hold readers' interest along with pointing out the utility of physical chemistry in the biological sciences. This mixture of the two disciplines is where a lot of modern scientific research is right now. Such techniques provided the tools needed to map the
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human genome. I still have not decided how best to teach physical chemistry here at my institution, but the author has provided a delightful resource that might push me in that direction. One can always debate what should and should not be included in such a text, but with the author's far greater background in this area, I nod to his wisdom. Literature Cited 1. Atkins, P.; de Paula, J. Physical Chemistry, 8th ed.; W. H. Freeman: New York, NY, 2006. 2. Noggle, J. H. Physical Chemistry, 3rd ed.; Harper Collins: New York, NY, 1996. 3. Berry, R. S.; Rice, S. A.; Ross, J. Physical Chemistry; John Wiley & Sons: New York, NY, 1980.
Michael P. McCann teaches chemistry at Mount Olive College, Mount Olive, NC 28365;
[email protected]. DOI: 10.1021/ed101051z Published on Web 11/02/2010
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