A laboratory program in physical chemistry - Journal of Chemical

A laboratory program in physical chemistry. Emil J. Slowinski Jr. ... (Audience):. Upper-Division Undergraduate ... Inquiry-Based / Discovery Learning...
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CHEMISTRY EMIL J. SLOWINSKI, JR. University of Connecticut, Storrs, Connecticut

T H E aims of the laboratory work in the usual undergraduate course in physical chemistry are probably well agreed upon. The students should become familiar with the methods of making physical measurements and with the application of these methods to experimental problems. The work should be made as challenging as possible to the student, and where feasible he should be given ~esponsibilityfor planning and executing experiments. Indeed, perhaps the most important aim is the development of proper approach to laboratory experiment, and hence to research. The degree to which these aims are met by laboratory programs varies widely, but on the average one would guess that results are not very satisfactory. Many factors make for difficulty in successful handling of the laboratory. One of the most important of these is the relatively large amount of specialized apparatus which the student must be called upon to use and understand. The apparent need for efficient use of laboratory time often makes for considerable overplanning of the experiments by the instructor. Equipment may he essentially completely set up, very detailed written instruction may he given, and a standard fill-in form for submitting the report may even he available. The obvious result of all this is surely efficiency of a sort but is often a complete failure to meet the real purpose of the laboratory. Students are simply overwhelmed by direction and rush through the experiment blindly, with almost no understanding of what they are doing and certainly with no feeling that they have conceived and planned the work. Very little thought is involved in their work and very little of lasting value is gained. With the hope that something might be done to achieve to a greater degree our actual aims, we have recently adopted a rather different approach to the laboratory program. Though our approach originated here, we find that the general principles are those which have been employed in several other college laboratories. Work in the fall term is centered about measurements on unknown liquids, one of which is given to each student. He is responsible for obtaining, by the end of the first ten weeks, values for ten assigned physical properties. The methods he will use, as well as the actual experimental procedures, are left to him to decide. As part of his work he is to submit a written report on each property which he has measured. The rewired measurements (at 30°C.) are:

density (two methods) viscosity surface tension (two methods)

VOLUME 34, NO. 7, JULY, 1957

normal boiling point vapor pres8ure molar heat of vaporization

refractive index freeeing point

specific heat molecular weight

Discussions of possible methods for making the measurements are available to the student in his assigned laboratory text ("Experimental Physical Chemistry," DANIELSet al., McGraw-Hill Book Co., Inc.). Use of other sources is encouraged, and in the course of the program students have used other laboratory manuals, issues of THIS JOURNAL, and on some occasions have gone to the original literature. Most of the students also own a chemical handbook and refer when necessary to the "International Critical Tables." Frequent discussions between students and laboratory supervisors are held regarding problems of technique and procedure. Students are allowed to work in pairs, doing both unknowns, since this seems to result in better efficiency and a better learning experience. Though it is not part of the assignment, students frequently, toward the end of the ten weeks, identify their compound, and hence are able t o check their results with the literature values. They are not informed, however, whether the identification is correct until their reports are graded, since the liquid is an "unknown" and we wish to put no pressure on the student t o obtain a "correct" result. Students may submit written reports on their work a t any time, but by the end of the ten-week period all reports must be in; late reports get no credit. The written report must include the following: a statement of the property which was measured, the method which was used, a discussion of the theoretical and practical significance of the property, the actual experimental procedure, the experimental results which were obtained, the calculations of the value of the property, and an analysis and estimation of the errors involved. Experiments in which calculations are incorrect are returned without a grade t o the student to be corrected and resubmitted. Equipment for the program has in many cases been constructed here, since it involves only rather elementary glassblowing. For our laboratory sessions, which average about ten students, the following equipment has proved t o be very adequate: six pycnometers, two Westphal balances, four Ostwald viscometers, three sets of capillary-rise apparatus, two du Nuoy tensiometers, an Abbe refractometer, two Mensies-type isoteniscopes, a halfdosen 500-ml. Dewar flasks. an isothermal (Bunsen) calorimeter, a small ( 5 ) Dewar calor&eter, and four ~ i c t ' o rMeyer setups. The unknowns are stable, pure organic liquids, 351

having boiling points between about 60' and 110°C. Suitable materials were found by scanning the organic chemicals section of one of the chemical handbooks. A better source might well be the organic chemicals catalogne of one of the larger producers, since there one can find available purities and also costs. A list of twenty-five compounds which have proved satisfactory is given below and could easily be extended. Some of the more common organic liquids (benzene, carbon tetrachloride, acetone, ethanol) have not been used as unknowns since too easy identification of the substance seems undesirable. About 150 ml. of sample is adequate for a11 the measurements. Organic Lipuids.Szlitable as Phgsical Pmperties Unknauns: acetonitrile methvl acetate methbl cyclohexane twt-amyl chloride methyl ethyl ketone sec-butyl alcohol methyl isopropyl ketone tert-butyl alcohol methyl propyl ketone tert-hutyl bromide methyl propionste n-butyl chloride isopropyl acetate cyclahemne isopropyl sleohol cyclohexene n-propyl alcohol dioxane isopropyl ether ethyl propionate n-propyl formate ethylene chloride triehloroethylene Buorobenzene hexane

The results obtained with classes given this assignment have been excellent. Student interest, which frequently lags in laboratory courses in physical chemistry, has been quite high. Many students appreciate the opportunity t o work on their own, and show real pride in good technique and in developing successful procedures. Written reports, as well as the experimental results, vary in quality but often show that the student has done some outside reading and has put some thought and effort into what he has written and calculat,ed. Certainly the experience of writing in technical language is valuable. The remainder of the laboratory course attempts t o continue the approach of the first ten weeks by assigning general problems and leaving the methods and details of procedure as much as possible to the student. For example, to complete the work of the first semester, each student does an experiment involving one of the colligative properties of solutions and, as part of the experiment, evaluates the molecular weight of an unknown solid. By the end of a year of working with such problems as these, many students demonstrate an ability to plan and properly carry out experiments of a difficulty well above that ordinarily encountered in undergraduate work.

CHEMICAL RESEARCH IN LIBERAL ARTS COLLEGES, 1952-56 JOHN R. SAMPEY Furman University, Greenville, South Carolina


CHECK of the 375,000 abstracts in Chemical Abstracts for the five-year period, 1952-56, will give as comprehensive a survey of research published by liberal arts colleges as is available. Not all abstracts in Chemical Abstracts, however, give the addresses of the authors, and some research published in borderline fields is not included (papers appearing in the voluminous medical journals particularly are often last to C.A.), but no other publication can make a more valid claim to the title, "Key to the World's Chemical Literature." An earlier survey of the pages of the Journal of the American Chemical Society for 192741 showed that liberal arta colleges contributed less than two per cent of the research published in this leading theoretical journal.' Only 62 liberal arts colleges published anything in the Journal of the American Chemical Society during the 15-year period. In contrast, a check of Chemical Abstracts shows that during the last five years 162 liberal arts colleges had 736 articles abstracted during the period 1952-56. The 7th Edition (1953) of the" College Blue Book" has been used ' SAMPEY,J. R.,J . Highel. Edue., 20, 208 (1949).

' SAMPEY,J. R., J. CHEM.EDUC.,27, 69 (1950).

to determine the liberal arts statns of the colleges. Institutions granting the Ph.D. degree, or that have professional schools of engineering, medicine, pharmacy, etc., have not been classed as liberal arts. Chemical research in liberal arts colleges is concentrated in a relatively small number of these institutions. Only 38 colleges averaged one or more articles a year for the fiveyear period, and yet these 38 accounted for 531 contributions, leaving 124 colleges to total 205 publications. A list of the most productive institutions is given in the table. The geographical distribution of these 38 colleges is as follows: 18 colleges in the North Central states accounted for more than one-half of the total (242); New England states had 8 institutions publishing 149 articles, and the same number of southern colleges published 102 papers, leaving 4 western colleges the remaining 38 articles. This distribution offers some interesting comparisons with that noted for liberal arts colleges contributing to the Journal of Chemical Education for the 15 years, 193448.2 One-half of the most productive liberal arts colleges are denominationally controlled, and one-half are JOURNAL OF CHEMICAL EDUCATION