Advances in Teaching Physical Chemistry - American Chemical Society

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Chapter 3

Decisions in the Physical Chemistry Course Robert G . Mortimer Professor Emeritus, Rhodes College, Memphis, TN 38112

A physical chemistry instructor is faced with a number of decisions: the goals and objectives of the course, the level of presentation, the choice of textbook, what topics to include, the sequence of topics, the balance between fundamentals and applications, the amount of homework to assign, the use of classroom time, and so forth. O f the students in the class, only a small fraction might intend to become physical chemists. The physical chemistry instructor must make his or her decisions in this context.

© 2008 American Chemical Society

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Decisions, Decisions The predecessor of this volume appeared in 1993, and covers a variety of topics. (1) The present volume also contains various schemes for improving the physical chemistry curriculum, as well as new suggestions for the laboratory portion of the course. There have been other workshops and meetings, including a workshop on curricular developments in the analytical sciences sponsored by the NSF and chaired by Prof. Ted Kuwana of the University of Kansas. (2) You, the teacher of physical chemistry must decide how to apply this large amount of information and the physical chemistry knowledge that you already possess. You should make these decisions consciously, based on the situation that you face and on your goals and objectives for the course. This essay is primarily an attempt by a retired professor of physical chemistry to comment on some of the decisions he has made in a career of four decades.

Goals and Objectives Your first decision involves the ultimate goals that you envision for your physical chemistry class and the specific objectives you want them to reach in order to work toward these goals. These goals relate to the development of your students' mental abilities and their mastery of physical chemistry. The mental discipline involved in learning any subject is valuable to a student, but this discipline cannot be learned in the absence of subject matter. Physical chemistry contains mathematical, theoretical, conceptual and descriptive aspects, and provides a coherent body of knowledge that is well suited to foster this mental discipline. A l l parts of physical chemistry cannot be included in a two-semester course, and you must decide what to include or exclude. Your decision will be informed by your goals for the course and by the population of your class, but the fact that a particular student will likely never use Raman spectroscopy does not mean that learning about Raman spectroscopy is of no value to him or her. A few decades ago some people might have thought that learning about nuclear magnetic resonance would have no value to a future physician. A possible set of goals for a physical chemistry course might be that the students would be able to: • • • • • •

Understand chemical and physical theories Apply theories to specific applications Organize knowledge into a coherent whole Analyze a problem and devise a solution scheme Apply mathematics to solving problems Compete in a global economy

30 • •

Work in a group Plan a laboratory experiment

Many of these goals would be the same for a course in any subject, and the students should learn that the value of any course goes beyond mastery of its subject material. B . F. Skinner once wrote, "Education is what survives when what has been learned has been forgotten." (3) Once you have your goals in mind you need to decide how best to assist your students in achieving these goals. This involves designing specific measurable objectives for the course, which should be chosen so that you can assess the extent to which the students have achieved these objectives during the course. A few possible objectives might be for the students to: • • • • • •

Be able Be able Be able Be able Be able Be able

to to to to to to

apply new descriptive chemical information give organized oral presentations write coherently assemble laboratory apparatuses carry out laboratory manipulations carry out an error analysis

The Population of Your Physical Chemistry Class Once you have your objectives in mind, you must analyze the population of your physical chemistry class in order to plan the accomplishment of your objectives. Most of your students will not become physical chemists. In a career of four decades, I worked with hundreds of physical chemistry students. Among these former students, I can now identify only a handful of professors of physical chemistry. There are several professors who teach other chemical subjects and a few high-school teachers. Those who work in industry work mostly with organic, analytical, or polymer chemistry. The largest group of my former physical chemistry students is made up of physicians and other health care workers. You should evaluate your students' preparation for the physical chemistry course. Most people agree that today's students are less well prepared than students of a few decades ago, but the students still come to you with widely varying preparation and abilities both in mathematics and in chemistry. Furthermore, their proposed career paths do not necessarily correlate with their preparation. I found it helpful to pass out a take-home orientation quiz on the first day of class. This quiz contained a few mathematics problems, a few physics and chemistry questions, a request for a list of all of the science and mathematics courses taken, and a request for a statement of the student's proposed career. Analysis of the students' responses could be used in planning the course.

31 The preparation for physical chemistry laboratory is a little harder to judge. Today's students seem less experienced in working with their hands than students of a few decades ago, except in the area of video games. I have used an initial experiment in which the students were required to carry out three simple measurements after assembling simple apparatuses, a technique that I learned from Ed Bair at Indiana University. Close observation of the students as they carry out such an experiment gives some information about their aptitude. This experiment also provided the opportunity to discuss data reduction, error analysis and report writing at the beginning of the course. Once you have designed objectives for your course and have determined what you can about the students in the class, you have more decisions to make. These might include the following: • • • • • • • • • • •

How much time to spend on the course The general approach of the course Topics to include or exclude The order of topics How to use class time How to relate to your students What kind of homework to assign Whether to give frequent quizzes How many and what kind of examinations to give How to determine grades What classroom tools to use

Time You have other things to do and must decide how much time you can spend on your physical chemistry class. You might have a number of research students working with you who need guidance. You might need to write a new grant proposal. You have other assignments such as student advising, committee work, department administrative work, and so on. However, you should not place your physical chemistry course at the bottom of your list of priorities.

The Approach of the Course You will have to decide whether to use a mathematical approach or a more conceptual or heuristic approach. The students in the United States of America are now less well prepared in mathematics than were the students of a few decades ago. This provides an incentive to make your physical chemistry course

32 less mathematical and more conceptual, and this might be appropriate for students who do not intend to become physical chemists. However, I believe that mathematics is the most important tool of physical chemistry, and that the ability to use mathematics will make your students more able to compete globally in the "flat world." (4) You will have to decide what to do i f your students' mathematical preparation is inadequate for the approach that you choose. You might decide to discuss mathematical topics with the entire class, as the topics are needed. You might decide to offer some mathematics help sessions outside of the regular class meetings. You might decide to refer students to one of the books that are available. (5) In any event, once you have decided on the level of mathematical sophistication that you want your students to achieve, you must help them to achieve it.

Choice of Topics Physical chemistry has been described as "everything that physical chemists happen to be interested in." You cannot cover all of it in two semesters, but a typical course might contain the following general topics: • • • • • •

Descriptive behavior of gases and liquids, Thermodynamics and its applications Dynamics, including gas kinetic theory, transport processes, and chemical kinetics Quantum mechanics, including atomic and molecular structure Spectroscopy Quantum statistical mechanics

There are other topics that might be considered, such as solid state theory and classical statistical mechanics. You must decide how much time to spend on each of your chosen topics. You can identify subtopics that you might omit or to which you can give only an introduction. One of the difficult decisions involves how much to teach about your own research area. You are obviously excited about this area, and will be tempted to spend too much class time on it. Another difficult decision is how much time to spend on topics of current interest such as nanomaterials and environmental chemistry. Your decisions should be guided by the composition of your class. If the class has a lot of premedical students and biochemistry majors in it, they are probably well served by a thorough treatment of thermodynamics and dynamics, and perhaps less well served by a thorough treatment of quantum mechanics and statistical mechanics. If the class is mostly composed of future chemistry graduate students, quantum mechanics and statistical mechanics are more important.

33 You must also decide how to approach computational chemistry. Many software packages are now available that allow the user to make sophisticated calculations without a detailed knowledge of the underlying theory. However, it is not productive of learning to let the students use the software as a "black box." You must decide how much of this theory to present and how to present it so that the students can appreciate what their calculations mean.

The Sequence of Topics There is an accelerating movement to place quantum mechanics and spectroscopy in the first semester, with thermodynamics and kinetics in the second semester. If all students take both semesters, this is not a bad idea, especially for future physical chemists. However, many colleges and universities require biochemistry or chemical biology students to take one semester of physical chemistry, and some of these colleges do not offer a separate one-semester course for these students. If a separate one-semester course cannot be offered, it is probably better for these students to place thermodynamics and dynamics in the first semester. I have seen one college catalog that specifies one semester of the standard physical chemistry course for biochemistry majors. This requirement was probably set up when thermodynamics and dynamics were taught in the first semester. However, the physical chemistry course at this college now has quantum mechanics and spectroscopy in the first semester, leaving the biochemistry students without instruction in thermodynamics and dynamics. The placement of statistical mechanics in the sequence is another issue. I think that careful treatments of thermodynamics and quantum mechanics should precede the presentation of statistical mechanics. This can be accomplished with thermodynamics in the first semester, quantum mechanics in the second semester, followed by statistical mechanics near the end of the course. If statistical mechanics is taught before thermodynamics or quantum mechanics, you must either provide a brief introduction to some of the concepts of these subjects at the beginning of the treatment or integrate it into the treatment.

Use of Class Time At one time, most college and university courses were taught as lectures, with students passively taking notes while the professor did all of the talking. Such an approach stimulates little student engagement and provides the instructor with little constructive feedback. There are other approaches that are more productive of learning. In one approach the class is divided into groups in which students work together during class time and are asked to report on the

34 work of the groups. It is hoped that one or more of the students will act as mentors for the other students in the group. Another approach is to use what used to be called the "Socratic method," which means that the teacher and the students carry on a dialogue driven by questions posed by the teacher. If you work out example problems in class, student involvement is increased i f the students know that they can be asked to carry out steps in the solution or to figure out what the next step should be. You can also ask the students to work problems in class, either individually or in groups.

Relating to Your Students There are several possible models for relating to your students: Y o u might be a "boss," a "coach," an "older friend," an "uncle," or a "buddy." As a beginning teacher many years ago, I subscribed to the "boss" model. I wore a coat and tie to class and called the students "Mr. Smith" and "Miss Jones." The students eventually asked me to call them by their given names, and I have tried since then to follow the "coach" model. It is important to build a genuine rapport with the students and let them know that you are genuinely interested in them, collectively and individually. However, it is probably a mistake to adopt the "buddy" model and to encourage the students to call you by your given name and "hang out" with them socially. You will have to decide how best to remain approachable but not be on the students' level. You should provide adequate office hours for individual and group consultations, and you might decide to tell the students that you will talk to them outside of your office hours whenever you are available. The important thing is to let them know that you care about their learning and that you and the students are on the same team.

Classroom Tools You must decide how to use the classroom tools that are available to you. Not many years ago, the only such tools were chalkboards, overhead projectors, and demonstrations. Many classrooms are now equipped with a computer and an associated projector. Some professors prepare slides that contain everything, including equations, so that they do not write on the chalkboard at all. This "canned" approach could encourage students to be passive and to regard the presentation as proceeding as though the students were not present. A better use of the computer and projector is to show slides to illustrate specific points and to carry out real-time simulations. Graphs can be created with values of parameters that are chosen by the students. Software packages such as Spartan and CAChe are sufficiently rapid that molecular modeling can be carried out in real time, allowing students to choose different molecules and different displays. Old-fashioned demonstrations can also be valuable. Building an electrochemical

35 cell in front of the students can illustrate some electrochemical principles. A toy gyroscope can illustrate some things about angular momentum as it precesses in the earth's gravitational field. The Journal of Chemical Education has a regular feature on tested demonstrations, and its website lists a number of books containing demonstrations. In addition to these tools, many useful tools are available on the internet. There are such things as programs that will solve the Hiickel equations on line, (