Student Problem Solving During General Chemistry Lectures Marlene S. Kolz University of Illinois Chicago Circle, Chicago, IL 60680 William R. Snyder University of Illinois Chicago Circle. Chicago. IL 60680 I n most college and university chemistry courses, lectures continue to be one of the main instructional methods used to transmit information to the students. Traditionally they are viewed as the most economical and convenient method by which chemistry teachers can present the fundamentals of their subject, emphasize key concepts, and model effective problem-solving skills. Unfortunately, the traditional lecture method has a t least three serious drawbacks: (1) If the class is large and diverse, the pace and content of a particular lecture may be appropriate for only a small percentage of the class. For instance, during any given lecture some students may become bored because they have already learned what the lecturer is explaining; a t the same time other students will lose interest because they cannot understand the lecturer's explanations. (2) During the traditional lecture, students are passive oarticinants-listening to the lecturer and taking notes. t'requrntly thih ixtivit)' drpenrrntrs to mindlessly copying down what thr lecturer s a w and writes.Thiz is in contrast ru Markle's ( I ) emphasis on the need for active participation of students during any instructional program. This activity is sometimes called "information processing" and takes the form of covert (mental) and sometimes overt (observable) responses by the student to each learning stimulus. Many lecturers assume that the students are covertly responding to their presentations; however, this assumption usually remains unverified since the lecturer rarely requires overt responses from his audience during the lecture. (3) Student efficiency and lecturer efficiency decline during any long, uninterrupted discourse. McLeish (2) points out that a parallel exists between the recognized sequence in work performance frequently descrihed by industrial psychologists and the performance of both lecturer and students during an hour-loni lecture. Ruth irquences begin with an initid period d h i g h perrormsnn.. This is fdlmvrd I,? a middlesax resultin:: fro; and fatigue and ends with a short return to - - - hiredom ~ ~ approximately the initiil high level of performance. During an hour-lone lecture the initial spurt lasts a .~.~ r o x i m a t eten lv minutes. '1.h; performance id hoih lwrurrr and itudents;hen craduallv declines until the last ten m i n u t e s d c l s ~ whrn s the. knal per?ormance spurt takes place. McLeish reports that this pattern appears to be virtually independent of individual lecturer and audience. While teaching general chemistry to large, lecture classes we became dissatisfied with the conduct and results of our lectures. Although requiring a great deal of preparation and effort, we noticed that our lectures did not always hold the students' attention during the entire lecture session. We usually felt a general waning of audience interest midway during ezch lecture, and although we carefully explained each important concept and problem-solving technique, subsequent examinations revealed that many of the students actually understood only a fraction of what we had told them. Realizing there was little we could do to individualize our lectures and that we could not change the lecture format of the UICC general chemistry courses, we decided that it might
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be possible to alter future spurt-sag-spurt performance cycles during lecture by introducing a number of lecture demonstrations and by causing the students to actively respond to our instruction once or twice during each lecture session. This report describes the latter activity. Two recent reports of student participation during lectures involved dividing the lecture class into small groups for the purposes of analyzing phenomenological data (3)and solving advanced problems related to the lecture topics (4). In view of the large size of UICC general chemistry classes (usually 300-500 students) this small group method did not appear feasible. Instead, a suggestion by Derek Rountree (5)seemed much more promising. To encourage thinking activity and student participation during lectures, he has proposed issuing the students a worksheet and stopping the lecture a t certain points so that they can complete some exercise that will help them to try out their understanding of the lecture up to that point. We realized this proposal was in agreement with McLeish's (2) conclusion that to improve the lecture the available time must be diversified by a variety of materials, pauses, and activities by the lecturer and students. Also, having the students answer questions and solve prohlems on a worksheet would he visible evidence of the covert responses that are necessary for successful information processing. (1) During the spring quarter of 1980, W. S. was scheduled to teach the second auarter of the vear-lone.. eeneral chemistrv . scquvnce oiferred tu science and non-scirncr miijuri at I IICC. Tht. t o ~ i c included s thermudvnnmi~s.electrot.hemistrv, kinetics,Bnd solution equilibria. ~ntici'patedenrollment was 350 students with the lectures scheduled for alarge lecture hall that required the use of overhead projectors for displaying visual information. Before the course began we considered whether the proposed lecture problems should he displayed on a projector or distributed to the students as lecture handouts. We were aware that most students would want to copy down each question if it appeared on a transparency. Since most of the planned questions involved quite a hit of writing, we were afraid this would require too much time, and so we decided to prepare lecture handouts with duplicate transparencies for the overhead projector. We also planned to distribute the lecture handouts on a weekly basis and to limit them to the front and back of a single sheet of paper. With 350 students, the ease of handout distribution and use as well as the amount of paper shuffling during the lectures were important considerations. Although our plan was based upon sound psychological principles, we were not aware of any current or past examples of its implementation. Consequently, formulating the lecture questions and actually using them during lecture were left up to our intuition. During the first week of class we unfortunately learned that several of our problems were not appropriate lecture questions. Two of the problems required the students to "discover" a rule by studying an example; we quickly discovered that too many of the students lacked the Volume 59
Number 9
September 1982
717
intellectual skills required to handle such problems. Another of these problems required the students to interpret a linear graph by estimating the value of two line segments and calculating the slope of the line. By observing the class while they attempted this prohlem we realized that the amount of information processing, hoth overt and covert, required for its solution was much greater than we had foreseen or desired. The result was that most of the students could not do the pruhlem in the allotted time. While we made these observations we also noted that some of our problems were quite successful. The students were able to write down an answer within two or three minutes and most of the observed responses were correct. After some consideration we decided that what made these problems so successful is that they followed the Evans, Glaser, and Homme (6) "ruleg" pattern of instruction that makes errors in resnondine most~unlikely.Each of these ruleg instructional patterns consists of a rule Yrul-") and one or more examples (e.g. = "eg"). The order of presentation and whether the rule or example is teacher-generated or student-generated varv from pattern to pattern. We-found that for Gcture problems the pattern RU EG EG (rule supplied example given example student tries) worked best, with the Lecture problem being the EG in the pattern. The discovery problems that had caused so many difficulties were of the EG RU type in which the student is asked to determine the rule from a eiven example. Evans, Glaser, and Homme predict this type of problem to he very error prone. For our purposes and in view of the large number of students in the class, we found it to he quite unsuitable. Problems 1and 2 are examples oflecture problems we assigned that follow the RU EG EG Dattern. After an explanation of electrolysis, half reactions, and cell reactions that used aqueous NaCl and H2S04 solutions as examples, Problem 1 was assigned to the class. Note that the students required no new information; however, they had to consult the day's lecture notes for the required half reactions in order to complete the problem. As with most of the lecture problems we used, this problem required from three to four minutes of class time. It gave the students an opportunitv to find out if they could identify the appropria&~equationsfor the described half reactions and combine them in an equation for the cell reaction. The net cell reaction (2H20 2H2 0 2 ) surprised the class and was a natural lead-in to a subsequent discussion of water's abilitv to conduct electricitv and the role of dissolved salts. Problem 2 is an examole of one of the kinetics lecture problems we used. Note that the amount of overt activity re: auired from the students is auite small comnared to the amount of covert or mental activity needed to choose an answer. If a planned lecture prohlem is going to take only a few minutes of lecture time, the amount of overt activity required for its solution is an important consideration. This kinetics problem was preceded b; both an explanation of how one goes about choosing a reaction mechanism consistent with a given rate law and one example. Again, the lecture prohlem gave the students an opportunity to "try it on their own." Near the endof the quarter the last set of lecture problems (dealing with solution equilibria) was not printed up for the students. Instead, the lecturer presented each one on the overhead projector. Since these questions did not take a long time to copy, this method worked as well as the lecture handouts. During each lecture session hoth authors observed that once the students became accustomed to having to "do" something during lecture almost all of them attempted to answer each lecture prohlem. Also, after the allotted time was up they anneared auite interested in how the lecturer solved each problem. he students frequently made additional cornme& or corrections on their own handouts and occasionallv asked the lecturer questluni that helped & ; ~ rt ~ pmisc~rncrptiunsor pi11polntt.d errors that m i q . d i h c students had n~:idr>. \Z'liilt~
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the students worked on each nroblem the lecturer (W. S.) walked around the lecture hall:~e soon found that watching different students trv each nroblem nrovided him with immediate and enlightening feedback. By the speed and correctness of their responses he quickly learned whether the preceding instruction had been successful. It also provided the opportunity to talk to individual students during lecture, giving additional directions, answering questions, or complimenting them on their work.
each half reaction and the cell reaction. Cell reaction:
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+ B C D circle the reaction mechanism consistent with the rate law: rate = k[A]' (a) A + B - C + D (b) B E (slow) 2A + E C + D (fast) (c) B E (fast) 2A+E-C+D(slow) (d) 2A E (fast) E B C + D (slow) (e) 12A E (slow) E B C + D (fast)
Problem 2. For the reaction A
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From these observations we concluded that insofar as achieving our two initial objectives-to increase student and lecturer efficiencv bv reducing the "sag" time during lectures and to increase the number ofopportunities the students have to actively respond to instruction during lecture-our use of lecture problems was quite successful. In general, the students anreed. Durine informal discussions manv of them said that hiving to do Lcture problems broke up t h e monotony and gave them an opportunity to find out during class if they understood that day's lesson. Some mentioned that they also used their lecture ~ r o h l e m as s examnles when thev tried their homework assignments. Having been favorahlv with these results. we . imnressed . have ul~sequentlyused lecture pnrhlems in o h r t lwmiatry classes. I'rohlem :l is an exantde uf one (11' the le;tur(. n r d h n s we later prepared for the irkroductory course of the UICC general chemistrv. sequence. Again, . . note that the amount of overt activity is quite small compared to the covert activity required to determine each compound's formula. We found that many of the topics in this introductory course such as chemical nomenclature, writing and balancing equations, and the Periodic Table lend themselves to this type of prohlem. Problem 3. Write the formula of each compound: sulfur dioxide sulfur trioxide phosphorus pentachloride dinitrogen trioxide W. S. has also used lecture problems during an organic chemistry course having a much smaller enrollment (about 60 students). For example, Problem 4 was assigned following a discussion of cycloaddition reactions which had included a number of examples. In this problem, students are given three compounds that could he synthesized hv this method and are askid to >up;est [he r e q u i k rr:~g(:nriforeach. Anutller lecttlrv prol~lernn5ked the students to propose a rnechs~iisnifor the rrx~rtic~n uf 3 thid and an aldehydr hllowing a d i s r u A m in lerture nmcernin:: the renction of :tlrohtJs and aldeh\,des to form acetals. The majority of students recognized the similarity of alcohols and thiols and were able to propose the eventual formation of a thioacetal. Just as in the general chemistry classes, we observed that lecture nroblems imnroved the conduct of the lectures in this organic chemistry course. The students actively participated in the lectures and showed great interest in the correct solution ~
of their lecture problems. Although we have not used this method in any other courses besides general chemistry and organic chemistry, our observations suggest that it could be used productively in more advanced chemistry courses as well. While we observed that our use of lecture problems did improve the lecture performance cycle by periodically requiring the students' active participation, it also has two drawbacks that must be mentioned. First. when the orinted lecture problems are prepared on a weekly basis, the iecturer has to have the lectures prepared a t least one week in advance. Of course, when the prohlems are presented on the overhead oroiector. this advance oreoaration is not reauired. Second. . . . . having the irudenrs work prdilems during lecture reduws rhr amount uf "mlkine time" available 10 t hc lecturer. Disi,xis~ied with the results ortraditional lectures, however, we cnncluded
Literature Cited (11 ~ s..r..k ~saran. e. "owigns fur ~nstructiondnerirners."
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Problem 4. Supply the reagents required to produce the following compounds by a cycloaddition reaction.
~~~.~~ . ow. 1.undon. 1974,~.120. ~
stipes, champaim, 111inoi3,
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161 F : v ~ ~ ~ I., .. I.. G I ~ %and ~ ~ ~ ,H
Volume 59
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Number 9
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