E. K. Mellon Florida State University Tallahassee. 32306
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Designing - - a Valuable Freshman Laboratow . Experience for the "Average" Science Major
The average first-year college science major. The characteristics of this much maligned person have changed over recent years. In the past the population of first-year science majors could be divided into two segments and many institutions provided different first-year chemistry courses for each. Those students who had had high school chemistry brought a set of well-defined skills and concepts to college, while those who had not could a t least be expected to read, write, and do arithmetic with some competence. Today fewer incoming science majors have had chemistry in high school, and the degree of preparation exhibited by thoae who have bad it varies from excellent to none a t all. It is safe tosav that today's college freshman, no matter what his background, is less able a t mathematics than the freshman of a generation ago. Many of the poorer students exhibit a desperate bravado, under which is hidden the certain fear that chemistw will undo them.'l'he situation is not totally hleak, however, since the average heginning student still brings a naive, hut all too easilv stifled. interest in chemistrv. The task of the instructor is to bring t k s heterogenous popkation to an acceptable level of competence, a t the same time destroying fear and nurturing interest. This paper examines the role played by the person who derigns the first lnboratory course in general chemistry in accomplishing this task. Most chemists todav are in ameement that the hands-on laboratory is a necessary part 'bf the freshman chemistry course. This was not always so. Inspired in part by an editorial in this Journal ( I ) , a symposium on the replacement of iudividual lahoratory work with lecture demonstrations in the general chemistry-course was presented a t the spring ACS meeting, New York, in 1935. Severe economic conditions across the nation had made rost cutting essential in colleges and universities. H. 1. Schlesinger spoke in favor of latwrato. wain. rips 12) while H. Hunt took the onnosite view (. 3.) Once equipment and personnel shortages during World War I1 inspired similar suggestions for the replacement of the general chemistry laboratory. Given the general agreement that individual laboratory work forms a necessary part of the first course in college chemistrv, the first ster, for the laboratorv desiener involves formulating objectives tor the course. ~ h e i obj&tives e can he classified as eeneral and yoecific. The set of eeneral ohiectives (2)is appearing written by ~ c h l e s i n ~iL1935 er ~
already published lahoratory program which is completely appropriate. A recent examination by the author of laboratory manuals in orint led to a conclusion in near nerfect ameement with the foliowing assessment dating from almost a i a l f century ago (4)' We are familiar with two extreme types of lahoratory manuals. In one, numerous short experiments of a descriptive nature are
outlined with little or no discussion of the .orincioles . of chemistrv. In the other type there arc only a i e w experimenrs mtlined nnn they are of either a qwntitltive nature ur in some other way de~ignedmd~velopthe theoretical side of the ruhject. The short experimental program is sufficiently challenging for poor students although boring for good students, while the quantitative one is almost invariahly too difficult for poor students. Faced with a heterogeneous student population, the lahoratory designer is practically forced to develop his own program, since no published alternative is appropriate. Laboratory Organization A more flexible laboratory organization is required to service a heteroeeneous student ~ o n u l a t i o nnronerlv. , Flexible laboratory organizational plans have been with us for some time. for examole. the 1931 "E1asticTask"of Brndt and Gerwe (6jand the 1'933contract plan suggested by Frank (7). Recent references to programs of similar flexibility are cited by Venkatachelam and Rudolph ( 8 ) .In most such pronrams the oreanization is desiened so that the ooor student is well groun2ed in fundamenials while the abie student is provided with excursions into what he sees as exciting work. A lahoratow operation plan which has been in successful ate is illustrated in the figure. use at the ~ l o ~ i d s ~ t~niversiry The plan is designed to assure at the vew least that the poorest student who passes the course is well g r k d e d in fundamental skills and concepts, while the best student h a heen challenged to the extent of his abilities. AU students enter the first content package (in our program the content is simple stoichiometry)
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I Apparently this classification of lahoratory programs was valid even in the 18706 ( 5 ) .
I ) To illustrate and clarify principles discussed in the claurroum. hy providing actual contact wth mntcrinls. 2) Tu y w e the student a feeling id the renl~ryofscicnce by an en-
counter with phenomena which otherwise might he to him no more than words. 3) To make the facts ofscience easy enough to learn and impressive enough to remember. 4) To e k e the student some insight into basic scientific laboratorv methods, to let him use hiaiands, and to train him in the; use. Implicit in several recent laboratory programs is a f$th general obiective: T o olace the student on his own in the lahoratorv.. bigiving him the principal responsibility for planning his work, as he becomes capable of doing so. The exact designation of specific ohjectives (loosely behavioral ohjectives) has been less commonly made until quite recently. T h e simplest out for the laboratory designer is t o adopt an
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CONTENT
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diagram of the laboatwy organization. Volume 54, Number 2,February 1977
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a t the noint marked entrv a t the ton of the firmre. A number of experiments with unkiowns a t tLe basic le;el are designed to test manipulative skills (i.e. weighing with the analytical balance and drying to constant weight) and associated concepts (simple mole calculations). These basic experiments resulted from the careful specification of objectives and the desien of practical tests to ensure the mastery of those objectkes. students who complete the unknowns acceptably move on to advanced level experiments while those students who have difficulty mastering the skills and concepts are led through remedial loops until the basic material is mastered. All students then pass through the block labeled "M & M" to another content package (in our program, acid-base chemistrvl. --", The block labeled "M & M" represents an experiment nhced in the scheme solelv for the sake of eniovment (inmore k i d e r n terms: reinforcement). All students are allowed to do these experiments, which were taken fromlecture demonstrations most requested over the years and no reports are required. Examples include the luminol and clock reactions, crystal mowing, and supervised horseplay with hydrogen filled balloons. Since all students may choose t o do the enjoyment experiments, the step-by-step instructions are explicit in the extreme. In general, the explicit character of the written instruction varies as the level becomes more advanced. The basic experiments are written in a step-by-step fashion. The B-level experimental writeups are moderately detailed, but make imnlicit use of the skill backeround nrovided hv the basic experiments. Instructions are quite sketchy at the A-level, reauirine that students use handbook data to desim - their own procedures. Student-generated suggestions for alternative experiments a t advanced levels are willingly accepted by course staff members. More substantial reinforcement than the enjoyment experiments is provided by the pacing of the course. Students are given explicit quality and quantity minima for A, B, and C grades on the fust day of classes. From then on it is up to the individual to plan his work so as to finish a t the desired grade level as soon as possible. Students are encouraged to have more tban one experiment in progress a t a time. The reward for an early finish is that the student is allowed to check out of lab when he has achieved the desired grade. This, in turn, frees bench space so thatstudents who have required extensive remediation, but wish a B or an A, can work extra lab periods. Choice of Course Content Three criteria should govern the choice of experimental content for the first laboratory course: simplicity, economy, and appropriateness. This discussion concerns the first laboratory course. Experiments which appear overly simple to the average chemist are frequently challenging in the extreme to the average freshman, while experiments which are in reality on the frontiers of chemical research (i.e., NQR spectros~opy,enantiomer separation, vacuum line syntheses, and the like) are likelv to backfire in that thev friehten and confuse. rather than enth;all, the timid beginner. ~ i author e has fo&d that the best estimate of the rieht level of comnlexitv for laboratorv " experiments results from experience gained ing large number of one-to-one tutoring occasions during and outside of office hours. Given the paucity of laboratory experience which the averaee student brines from high school, it is almost impossible to oversimplify i h e first llboratory: Economy in laboratory operation is a matter of concern in these financially troubled times. An inventory of equipment on hand irequently suggests operating economies. For example, the end of the 60's found the FSL' general chemistry laboratories well stocked with single-pan analytical balances. Thus instructions ~e witten SO that students perform simple stoichiometry experiments with half-grnm, rather than 3116 I Journal of Chemical Education
gram, quantities. A second example: we chose to have students monitor p H in the acid-base experiments with a universal visual indicator (9)2rather than with p H meters. Primarily this is because it allows students to work with l-ml quantities of reagents. There are other reasons for the choice: the color displays are dramatic and esthetically pleasing, and the visual indicator gives the students a concrete (in the Piagetian sense) experience with acid-base chemistry. A third example: centrifuges were kept in storage after thidemise of the qualitative analysis course, and they were recently reactivated permitting the separations involved in a K , experiment to be done with small test-tube quantities. A generation has passed since Brown and Rulfs wrote (11) However, at the present time a large majority of schools have to all practical purposes ceased offering instruction in inorganic chemistry. These schools are graduating "professional chemists" e s reactions of simple common who do not know the ~ r o ~ e r t i or chemicals. who cannoi su-eeest .... means of vrevarin~ . . .or purifying simple inorganic subsrances, and who do not recognize the hag ardr involved in certain reartions of common inorganic reacents. ~
T o the extent that the quotation has remained a valid comment, i t suggests that not only are students being short changed on descriptive chemistry, but that this is a second generation effect. I t would seem appropriate to include a heady dose of descriptive chemistry in the first laboratory course for the following reasons. First, it fills a gap in the usual chemistry undergraduate curriculum as suggested by Brown and Rulfs. Specifically a knowledge of descriptive inorganic chemistry is useful in the organic and analytical courses which usuallv follow the general chemistry course. Second, much information complementary to that presented in the classroom can be woven into the written instructions for the laboratory. Third, the proper choice of descriptive material can form the background for a qualitative analysis experiment or scheme a t theknd of the course. Summary It has been pointed out that the science major population in the first-year course is becoming more heterogeneous. This suggests that more complex laboratory organizational plans should be devised to train all students adequately while a t the same time challenging better students. An example is presented which offers flexibility in pacing. This flexibility can function as a powerful inducement to hard work and careful nlannine on the nart of the student. Choice of laboratory content is also important in maintainine student interest. The content should be simple, economical, and appropri@e. One appropriate choice for the content area is descrintive inoreanic chemistry. Individual scheduling constraints and preferences make it almost certain that the details of the program presented here are usable only a t FSU. However the-suggestions about flexibilitv in oreanization and a~propriateness of content should .. be ge"nerall; applicable.
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Practical Notes A series of practical details is presented for those readers with a more tban passing interest in the design of the first laboratorv course. When FSU went on the quarter system several years ago. the schedule of two semesters of lecture work accompanied by lahoracories meeting four hours a week was abandoned. In its stead the following rourse schedule was adopted.
2 We were unable to locate a supplier of meta methyl red indicator so it was replaced with N,Ndimethyl-p-(m-tolyl~zo)aniline (Eastman 7793). Also commercial suppliers are at present out of sym-trinitrobenzene so it was synthesized by the oxidation and decarhoxylatian of sym-trinitrotoluene(10).
Quarter one:
lecture (3 hours per week) Quarter two: lecture (3 hours per week) Quarter three: lecture (3 hours per week)
lecture recitation (1 hrlweek) laboratory (6 hrslweek) laboratory (6 hrslweek)
The second-quarter laboratory is the one described in this paper and the third-quarter laboratory is a volumetric quantitative analysis course with a similar organizational plan. Since students receive only two-quarter's credit for six laboratory hours, we feel it only fair to hold outside work to a minimum. Since we would rather have the student spend his outside hours carefully planning his laboratory work, we require no written laboratory reports. Rather,students turn in carbon copies of pages in their lab notebooks at the end of earh period. When a student finishes an experiment, he summarizes his d ~ t and n ronclusions in his lat, notebook, and submits the rarboli COPV. We feel that the use of unknowns ensures student unde&anding equally as well as the requirement of laboratory reports. ~ l t h o u g hwe have a room scheduled for a one-hour laboratory recitation each week, it is used sporadically. We find students extremely anxious to get t o bench work at the beginning of each period (early checkout!) and it is verv difficult persuade them to s t o p work a t the end of the period. Therefore, we have one formal recitation at the first lab meeting toexplain the mumeorganination, and other meetinp only when thestudentsdemand them. Thisplaces the TA at an advantage in that he always has an audience which actively wants to hear what he has to say. The TA's are previously trained in video recorded microteachine" sessions (12). . . We considered moving to completely open laboratories, but settled on the plan described above in the interest of staffine eronomy, parti'cularly in quarten where laboratory enrollme; is small. The plan shares many of the advantages of open labs and has the additional advantage over openulabs in that i t rewards the student for planning his work carefullv and usine his laboratory time efficiently. ' The first experiment in the sequence (even before the first content package) is the measurement of the hydrogen Balmer spectrum with a very simple spectroscope (13) followed by an enjoyment interlude with the luminol experiment (14). These experiments are placed first because they require that laboratory rooms be darkened. Although the Balmer experiment can be classified as inorganic reaction chemistry only by a wild stretch of the imaeination. it was retained from an earlier laboratory program becausk of its popularity with faculty. The content package on simple stoichiometry begins with a concrete experience with a very simple reaction, the thermal dehydration of CuS045H20. Students observe the color change and the condensation of water vapor near the top of the test tube. Thev wateh the white product turn powder blue on the bench t o p in the Florida h;midity ove;a two-hour period, then they dissolve the CuSOd in a small amount of warer on a watc&lass and grow cryst&. What seems at first view an alarmingly simple experiment whose results should be familiar to every literate adult, turns out to be enjoyable and profitable for the average student. Students are then checked in the usual way on precision in weighing, and monitored on accuracy in weighing by having them determine the percent water in an unknown hydrate. Remediation is prescribed for those who cannot complete these experiments acceptably. The basic level in the stoichiometry package continues with experiments based on the activity series of metals. Students first do the Zno-Cu2f replacement reaction using their home grown CuSO4 crystals. They then study the weight stoichiometry of the Zn-HC1reaction (15), a slightly more complex reaction where product separation is, however, still simple. The final basic experiment involves the introduction of K , by way of the preparation of PbCr04 from excess K2Cr04and
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an issued sample of P b ( N 0 3 ) whose ~ weight is known to the instructor. The solid is washed by centrifugation and decantation, in this case the color of the washings being a criterion of purity. Students report the weight and numher of moles of PbCrOa produced, and the combined weight of KN03 and KzCr04 recovered from the washings, and then estimate the weight of KN03 and of KzCr04 in the washing residue using stoichiometric calculations. At the B-level, students analyze an unknown mixture of BaClp.2Hp0 and NaCI. Atthe A-level, students devise a fractional crystallizstion scheme to separate and weigh the crvstalline KNO* and KzCr04 fromthe residue from the washings in the P ~ C ~ O ~ experiment. They then devise a wav toestimate -~ u r i -t v f othe r products (hint: add Pbz+). In order to cut costs, students are encouraged t o form groups in performing the enjoyment experiments. The experiments involve preparing small K2Cr207 and KzS04 crystals ("artificial jewels") on shaped pipe cleaners (16) and growing large mixed alum crystals. The content ~ a c k a e on e acids and bases begins vervsim~lv , . < with litmus paper tests. Students are then ebiluated for volumetric dilurion skills bv hanne them measure. usine a mixed indicator (9),2the pH's of vazous strength ~ a ~ ~ - HCI a n d solutions which thev. . orepare . from 0.10 M stock. Color blind students are, of course, provided with p H meters. They then do K, and percent ionization calculations from p H measurements on acetic acid, acetate ion, ammonium ion, and ammonia solutions of various strengths prepared from 0.10 M stock. The effect of dissolved COz is dramatically illustrated by having them bubble COz (from Dry Ice) through freshly boiled distilled water and various acidic and basic solutions. The advantage of the in situ mixed indicator over paper p H indicators is dramatically revealed in this experiment. Students then study hydrolysis, amphoterism, buffers, and the common ion effect a t the B-level. At the A-level, they study the thermal decomposition of AIClyGHpO which yields HC1 amonn the naseous ~roducts. For-the eGjoymeni experiment, the students are encouraged to form groups . tostudv the traditional iodine clock reaction. varying concentrations, temperatures, etc. The content package on gases contains only three experiments. The basic level experiment involves the production and measurement of gaseous H2 from the reaction of weighed amounts of Al with NaOH (most students are familiar with amphoterism by this time). For the A-level experiment, students form groups in which each is assigned an HN03 concentration. Each student then prepares an HN03 solution by dilution of concentrated acid and determines the amounts of -~ ---.. --.. .NO and NO2 produced by the oxidation of a weighed sample of Cu (17). to ~-~~ ~. . Class data are nooled. and students are asked compare results when the reaction is run under air with those produced under a CO? atmosnhere. The eniovment e x ~ e r i Lent consists of organized hbrseplay with0h;drogen filled balloons. The final experiment involves characterization of an unknown mixture using all the skills accumulated over the quarter. Laboratory instructions are reproduced in the department and issued from the stockroom. The charge for written materials covers only the cost of reproduction. The average grade in the course is a high B. Failing grades are reserved for those few students who do not attend. The rare student who tries bard, attends regularly, and still does not complete enough work for a C is given an incomplete and completes his work in a subsequent quarter. There are no written quizzes in the course as presented. Each TA is supplied with lists of oral questions concerning the experiments. The results of the oral questioning are used in deciding borderline cases. TA's are prepared in tutoring, reinforcement, and questioning skills with the Project TEACH ~~~
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Acknowledgment
The author would like to thank the departmental advisory committee for aid in choosing the organization and content: R. J. Light, R. J. Clark, D. F. DeTar,R. E. Glick, K. B. Hoffman, and R. J. Keirs. He is indebted to P. W. McLain for help in working out practical details and to Professor D. W. Brwks, the University of Nebraska-Lincoln, for providing an opportunity to test the Project TEACH m o d ~ l e s . ~ Literature Cited (11 Reinmuth. Otto. J. CHEM. EDUC., 9.971 (19311. (2) Schiesinger, H. l.,J.CHEM.EDUC., 12,52411935J. (3) Hunf.H..J. CHEM.EDUC.. 13.29 11936). (4) Maeser, S.. J . CHEM. EDUC., 4 177 (19291. (51 Roren,S., J.CHEM. EDUC.,33,627(1956),35,209,423(1958J. (6) Bradt, W. E., and Gerwe. R. D., J. CHEM, EDUC., 8,1574 (19311. (71 Frank.J. 0 ,J.CHEM.EDUC., 10,556 (1933). (3) Venkstaehelsm, C., and Rudolph, R. W., J. CHEM. EDUC., 61,479 (9) Richardson,F. R., J. CHEM EDUC.,33.517 (1956).
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(101 Vogel, A. I.. "A Textbook of Practical O~ganicChemistry:' Third Ed., Longmans, London. 1956. pp. 753and 965. (111 Brow, H. C., and Rulfs, C. L., J. CHEM. EDUC., 27,437 (19501, presented as a part of the Symposium on the Placeof InarganicChemistry in the Undergraduate Curriculum. 116th National Meetine. ACS. Atlantic Citv. 1949. Dence, J.B., J.EHEM.EDUC.,48;674 (l97ll. Mellon, Edwards, R.K.,Bmndt, W. W.,andCompanion,A.L, J.CHEM.EDUC.,39.147(1962): Companion,A., and Schug, K..J. CHEM. EDUC., 43,591 (1966): Harris, S. P., J. CHEM. EDUC.. 39.319 119621. Bailey, P. S.. Bailey. C. A.. Anderson. J., Koski.?. G.. and Rschateiner, C., J. CHEM. EDUC.,52.524 (19751. Wolthus, E., DeVrias, D., and Poutpma, M.. J. CHEM EDUC., 34.133 (1957). Fehlner, F. P.,J.CHEM.EDUC.,33,449 (19561. Nechamkin. H.. J.CHEM. EDUC..29.92(1952).
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The year's crop of TA's was trained in questioning, tutoring, and interaction analysis using the Project TEACH modules. The Project TEACH materials were prepared under a grant from the Exxon Education Foundation to the University of Nebraska-Lincoln. Further information can be obtained from the Project TEACH Materials Coordinator, Department of Chemistry, University of NebraskaLincoln, Lincoln, NE 68588.
