Teaching Physical Chemistry - American Chemical Society

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I. Amdur Massachusetts Institute

of Technology Cambridge

Teaching Physical Chemistry At the Massachusetts Institute of Technology

At the Massachusetts Institute of Technology a three semester course in physical chemistry is offered to students with a variety of professional interests. Although this course may not be adaptable to all schools, its content is presented here as an example of the department's concept of a thorough and rigorous physical chemistry sequence for an undergraduate curriculum. Of a total of 350 students who enroll for the first semester of the sequence, about 40 are junior chemistry majors, and about 200 are sophomore physics majors. Most of the remainder usually major in biology, chemical engineering, metallurgy, or business administration, while a small number, about 20, are graduate or special students whose physical chemistry backgrounds are Presented ss part of the Symposium on Teaching of Physical Chemistry before joint sessions of the Divisions of Physical Chemistry and Chemical Education at the 148th National Meeting of the American Chemical Society in Chicago, Illinois, August 31, 1964. ' Other MIT staff memben who teach the course described here. and who have made major oantributions to it4 development are C. W. Garland, G. G. Hammes, J. L. Kinsey, R. C. Lord, I. Oo~enheim.D. P. Shoemaker, W. R. Thorson and J. S. Waugh, all of'the phy&cal chemistry staff.

weak or nonexistent. I n the second semester the enrollment drops to approximately 150, since the physics majors, for the most part, do not continue to take physical chemistry. Finally, in the third semester, the course is reduced to about 50 students, consisting primarily of chemistry majors, although a few chemical engineers and biologists also elect this part of the sequence. Certain students majoring in chemistry under a physics option, may substitute an additional physics course which includes many of the topics covered in the third semester of physical chemistry. Lecture Course

There are three one-hour lecture sessions each week, and all students attend the same lecture. Each student also attends one recitation hour each week; a sufficient number of recitation sections are scheduled so that no section has more than 25 students. These recitations are used to discuss or amplify topics which have been presented in lectures or which are involved in the regularly scheduled problem assignments. Responsibility for the lecturing and administration of the course in a given semester is rotated among - the physical . . chemistry staff. The principal text is the third edition of "Physical

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Chemistry" by Walter J. Moore. I n addition, each lecturer is free to suggest supplementary texts. Although a great deal of information is often presented in lecture, only a reasonable return is expected on examinations, and the students are encouraged to regard some of the additional material as background for future advanced courses. Other portions of the lecture material are used to illustrate the type of science which is professionally and culturally exciting because of the elegance of the logic, the rigor with which the physical concepts are treated, or, conversely, the cleverness with which useful approximations, empiricism or intuition have been used where rigorous formalism would contribute little to an understanding of fundamental principles or experimental observations. Occasionally, a lecturer may make a presentation based on an over-simplified model, and thereby obtain results which are only partially ;did. I n such insrnncrs, thc insdeqwi~irsoi the treatumlt and t h r 1imitation.rof the rt:suI~sarc pointed out to the lecture session in an attempt to improve the students' power to reason logically and their ability to detect errors or fallacies. The staff has found that the better students are stimulated by being exposed to somewhat more than they can absorb in a first course. Failures, which are a function more of motivation than of any other single factor, range from 4 to 10 percent, and are no higher than they were in previous types of physical chemistry courses which were more conservative in character. The first semester of the course is confined to a rigorous treatment of classical thermodynamics. Its content is described in the Institute catalog as: "first and second laws of thermodynamics; properties of solutions; phase equilibrium; chemical equilibrium and the third law of thermodynamics; ionic equilibria; and voltaic cells." Dynamical properties are covered in the second semester, and the major topics include: elementary kinetic theory and statistical mechanics; transport properties of gases and liquids; and rates of chemical reactions. The statistical mechanics is developed to the point where the student is able to calculate thermodynamic quantities introduced in the preceding semester. Throughout the semester the relation of intermolecular forces to macroscopic properties is emphasized. Examples are deviations from ideal gas behavior, temperature dependence of transport properties of dilute gases, and lattice energies of crystalline solids. The third semester is devoted entirely to introductory quantum chemistry, elementary atomic spectra, particles and waves, wave mechanics, atomic structure and the periodic table, valence theory, experimental methods of determining molecular structure with particular emphasis on molecular spectra, structure of crystals and liquids, and photochemistry. After completion of this three term sequence in the first semester of the senior year, a chemistry major is well prepared for any physical chemistry graduate course he may wish to elect during his final semester. Laboratory Course

The laboratory course is entirely separate from the lecture course, and it is graded separately. "Experiments in Physical Chemistry" by D. P. Shoemaker and 192 / Journal o f Chemical Education

C. W. Garland is the principal text. Occasionally, supplementary material is provided in mimeographed form. All chemistry majors take the first term of the laboratory at the beginning of their junior year. At present, about an equal number of chemical engineers are also enrolled. Every attempt is made to correlate the laboratory with the lecture. The student is required to study the background material for an experiment before he comes int,o the laboratory. To make sure that he is familiar with the procedure, he must snhmit a brief outline of the experiment to the instructor before he starts the actual work. I n addition to his preliminary st,udy of the experimental procedure and his preparation of the outline, the student is required to enter his experimental results in a regular research notebook which provides for a duplicate data sheet. Procedures used in original research are followed, such as insistence on the entry of all experimental results without erasures. During the first semester there are weekly four-hour lahoratory periods, 15 in all. Eight weeks are allotted to classical experiments; the final seven weeks are devoted to contemporary and sophisticated elective experiments. The classical experiments required in the first semester include: constant volume thermometry, in which temperature is measured as a function of pressure in a constant volume system; therrnochemistry, heat of neutralization, heat of ionization and bomb calorimetry; partial molal volume; the equilibrium constant for the formation of the triiodide ion; molecular weight determination; freezing point depression; and the effect of an inert salt on the solubility of a sparingly soluble material (silver acetate), as an application of the Dehye-Hiickel theory. Of the eight elective experiments offered, the student must complet,e four. The eight are the spectrum of hydrogen in a discharge tube measured with a Hilger spectrometer, the spectra of dyes measured with a Reckman spectrometer, a distillation curve, surface t,ension measurements, a Joule-Thonlpson expansion experiment, a Gouy balance experiment to determine magnetic susceptibility, a dielectric constant measurement using heterodyne heat circuits, and the measurement of dipole moments. I n the following semester there are 14 five-hour laboratory periods, and, again, classical and contemporary experiments are included. Six classical experiments are required of each student. I n addition, he may elect five experiments of a rather nonclassical character from a group of eight. The required classical experiments are measurement of a transference number by the moving boundary method; a conductance experiment; the determination of the activity coefficient of an electrolyte by measuring the emf of a reversible cell; the determination of the viscosity of a gas from its rate of flow through a capillary; kinetics of the iodine clock reaction; and the hydrolysis of acetal, where the rate of reaction is followed dilatometrically (change of volume with extent of reaction). The elective experiments are the intrinsic viscosity of a polymer; a diffusion experiment in solution; the vapor pressure of argon, and the determination of its latent heat of vaporization; the infrared spectrum of sulfur dioxide; t,he band spectrum of nitrogen, where the student obtains the spectrum and then analyzes it;

the analysis of an X-ray powder diagram; kinetic study of an extremely rapid reaction in which the iron (111) ion is complexed with thiocyanate and the reaction is followed spectrophotometrically as the mixture flows down a tube; and study of a helix-coil transition in polypeptides by measuring optical rotation as a function of temperature. These last two experiments were originally suggested as special projects, but are now electives. During the second semester a student with average grade of B or better may choose three elective experiments and a special project instead of five elective experiments. Usually about six students undertake a special project which is really a small-scale research problem. These projects have included: the thermal decomposition of solids; a surface balance experiment involving a Langmuir tray apparatus; the dielectric dispersion in a polymer solution; an adsorption experiment which uses a quartz balance; a shock wave experiment; and the two experiments previously mentioned as electives. A student who works on a special project must study original literature, write up a procedure and carry out the experiment independently. He has the assistance of a graduate student, and any member of the physical chemistry staff is available for

consultation. Although the staff may offer suggestions, the success or failure of the experiment depends entirely upon the student. Conclusion

The physical chemistry st& is well satisfied with the flexibility of the curriculum described above, and with the opportunity which it affords for developing a numher of important topics in depth. Other departments, such as chemical engineering, whose students are enrolled in the course, have also expressed enthusiasm for the content of the present sequence, which has now been through two cycles. As a result of the experience of the different staff members who have taken charge of the various parts of the course, improvements and modifications have been easily and informally incorporated. The present thinking of the physical chemistry staff is that since students a t M.I.T. receive intensive training in mathematics and physics in their freshman and sophomore years, the sequence of physical chemistry courses, both lecture and laboratory, could well be started in the second semestel of the sophon~oreyear. The student could then apply his basic knowledge of physical chemistry in later courses iu organic, inorganic and analytical chemistry.

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