Some advice we commonly give to students is that the best, if not the only, way to learn chemistry is to work through problems. Among instructors at all levels it is also widely known that one does not truly learn a subject until you have to teach it. To these we now know to add, “You don’t really know how to teach physical chemistry until you work through one-thousand problems and write the solutions for publication.” Of course it helps that those problems come from an author who possesses the wide-ranging command and deep understanding of physical chemistry that Raymond Chang does. Reading his textbook and working all the problems in it has revealed to us connections previously undiscovered and has improved our own mastery of the material. Professor Chang reviewed all the solutions as we wrote them, and our electronic discussions with him throughout the process were extremely valuable. We were privileged to work with him, once again for one of us and for the other, for the first time.
It is important to the authors of this solutions manual and to Professor Chang that it is written by faculty members who actively teach physical chemistry. This allows the book to adopt the same conversational style that we use in our own classrooms, with answers explained and assumptions discussed. Only for the most straightforward, often definitional problems, are the answers merely quoted. Our goal is that the manual combine the vitality and excitement of modern physical chemistry with strong, effective pedagogy.
We have made every effort to ensure consistency in the values of physical constants used, both internally and with those given in the textbook. Likewise, choices for symbols and units were made with care and hopefully consistency. We do have a word to say about significant figures, since every measurement has an associated uncertainty that must be considered when comparing results from different experiments or those of experiment with predictions from theory. The appropriate number of significant figures is determined by the data given in each problem. So, for example, if a mass is given as 1.78 g, then the answer to the problem should contain three significant figures. Quantities given as “1 mole,” or “5 L” are taken to be exact. Intermediate calculations are done retaining one extra digit, and the final answer is rounded to the correct number of significant figures in the final step. If a result from a previous part of a problem is used in a subsequent part, the value with the extra digit is used. In such cases, the answer to the earlier part would look similar to “45.678 kJ mol-1 = 45.68 kJ mol-1,” where the first value given is used later in the problem and the “correct” answer is the second. Of course, every rule has its exceptions, and we did choose to be somewhat more flexible in problems involving exponentiation and logarithms. (Do note that only those digits to the right of the decimal point in a common logarithm are significant. Those to the left merely set the value of the exponent in scientific notation.)
We thank Jane Ellis of University Science Books for keeping us on task and for helping to assemble the production team that transformed our LaTeX manuscript into a welldesigned publication. Many prefaces close with the authors expressing gratitude for understanding spouses who provided moral support during the preparation of the manuscript, even though they had no direct connection with the project. In this case, however, each author is grateful for a partner who is not only a wonderful spouse, but a most convivial coauthor as well.
Helen O. Leung, South Hadley, MA
Mark D. Marshall, Amherst, MA