Ruth Chabay and Stanley G. Smith University of lllinols Urbana. 61801
The Use of Computer-Based Chemistry Lessons An individualized component of a large lecture course
The PLATO IV computer-based teaching system ( I ) is used as a self-vaced. individualized comvonent of a number of large chemist& coui-ses a t the ~ n i v e r i i of t ~Illinois. The role of PLATO in these courses is twofold: first, it urovides interactive individual instruction on the basic cou;se material; and second, i t furnishes an automated course outline, a weekly assignment schedule, answers to exam questions, a communication medium between students and the instructor, and a report for each student on his grades and class standing. Both aspectshave heen tested for several semesters, and they have been enthusiastically received by students. The PLATO instructional lessons developed a t the University of !Ilinois are written in a variety of pedagogical styles and cover a wide range of topics. The lessons include tutorial dialoes between comnuter and student. animations and other comd;ter graphics; simulated experiments, open-ended ) vroblems. chemical games. and uroblem drills. svnthesis (.2.. In most cases a single lesson inclides severai of these comuonents. In a one-semester basic chemistw course offered for students who have had no general chemistry in high school, or whose chemistrv background is weak. PLATO lessons cover much of the basic iheory&d allow students to practice solving prohlems, giving immediate feedback on mistakes, and individual help when needed. For example, in a PLATO lesson on PLATO helps the student construct the Aufbau principle (3, the electronic configurations of the first 20 atoms, elucidating the Pauli exclusion principle along the way. After the student, with PLATO's assistance, has built up the configuration of Ca, he then works a set of problems in which he must fill in the electrons for a given atom by touching the location of each electron. In another group of lessons, students develop the ideal gas laws through simulated experiments (4) and then practice solving problems. Students use the touch-sensitive display screen to work out the necessary algebra as in Figure 1,then proceed to solve numerical prohlems, getting help from PLATO if they need it (5). Other PLATO lessons used in this general chemistry course cover hasic theoretical principles and'give students individual help working prohlems on other topics, including the metric system and scientific notation, nomenclature, basic atomic structure, ionic and covalent bonding, chemical formulas, halancing equations, stoichiometry, and chemical equilibrium (6). In addition, some students take their weekly quizzes on PLATO, generating more time for questions in their discussion sections. In the first semester organic chemistry courses, PLATO lessons cover each major topic in the course: nomenclature, optical activity, conformational analysis, chemistry of various functional groups, electrophilic aromatic substitution, nmr and ir spectroscopy, and multistep synthesis (7). In these courses, the PLATO lessons are assigned as homework, and a student receives several points for each lesson he works. Overall, as in the general chemistry course, the PLATO scores constitute about 10% of the total course grade. Tvuically, students in these courses spend about 2 h;/wk on PLATO, although since each student is able to work a t his own rate and to revLw any material he wishes, there is a large variation in the time spent by individual students. For example, though on the average students spent about 35 hours on PLATO during the course of one semester, some students spent up to 80 hours working and reviewing PLATO lessons.
Figwe 1. A display from a lesson on the applications of the ideal gas law. Here thestudent has been asked10 solve for V Plato has indicated errors inlhestudent's responw hv crcca ng 0.1 I r e o in the oenunl niltor an0 nalcallng tnal somelh nq is m srmg n llle nmeralor Tne z1.u~ nl rs.% reqLerlen help, sathc ~
~
~~
solution to the problem is displayed.
Figure 2. After the student has assembled the apparatus for the dstillation,he must connect the cooling water, add a boiling chip, and then warm the oil bath, and collect fractions as material distills. Many of the organic chemistry lessons use simulated experiments to provide the experimental background for important concepts. For example, in an organic chemistry lesson nn . -suhstitution and elimination reactions? a student must perform a set of simulated experiments to determine the dependence of the rate of reaction (n-butyl bromide with sodium ethoxide) on the concentrations of the reactants. He then ~ which prowatches animations of the E7 and S N reactions duce the tw~dit'frrt.ntprud~~c;s. After repeating the same kind of e x ~ e r i m e n t fii m the rmctivn rd t.butvl hrutnide u,ith iodium ethoxide, and watching animations of unimolecular suhstitution and elimination reactions, the student is led through a discussion of the stabilities of various types of carbonium ions. Volume 54, Number 12. December 1977 1 745
Other organic chemistry programs are directly related to laboratory work which the students do themselves. For example, a lesson on fractional distillation (91,Figure 2, allows the student to work through the operations involved in setting up the apparatus, controlling the distillation temperature, and collectine fractions. In a senior-level qualitative organic analysis laboratory course, students often spend the first three to four lab periods on PLATO, first reviewing basic wet chemical and spectroscopic analysis techniques, then developing logical strategies for the identification of unknown compounds (10). In all of these courses, students usually work on PLATO a t any time convenient for them, without the supervision of an instructor. A student signing on to PLATO sees an index of lessons appropriate t o t h e current week's work, and may choose to work any of these lessons or to review lessons he has previously completed. If the student ended his last PLATO session without completing a particular lesson, he is given the choice of resuming at the same point in the lesson, g~,ingback tu the beeinnine. Oftrn " -. or choosing another lrsson altogether. the course instructor sets up an automated curriculum index a t the beeinning of the semester, so that as each new week begins th;! student is shown an index of that week's lessons, with an option to review previous ones or to work ahead if he completes his assignments early. A generalized lesson management system available to all PLATO instructors allows an instructor to decide what the criteria for advancing a student to new lessons shall be, and to make special assignments for individual students if appropriate. PLATO itself plays a significant role in gathering both subjective and objective information on lesson functioning to aid in evaluation and revision of lessons. The computer provides an on-line message facility for communication between students and instructors, and also administers opinion auestionnaires. Ohiective data on the oerformance of lessons are automatically cblleded as students work through lessons. Data includiue both tabulations of student resoonses "iudeed "incorrect" and statistical analyses of the behavior of the lesson with a large group of students can suggest revisions which would improve the teaching effectiveness of the lesson. Often, authors familiar with the usual chemical phraseology do not anticipate variations in wording which students tend to use. In a iesson on valence electr'ns (111, for example, students were asked to type the symbol for the ion commonly formed by CI. Collecting responses judged incorrect by the lesson revealed that many students typed "CI-I," while the lesson recognized only the response "CI-," so the lesson was changed to accept "CI-1," as well. On the other hand, another common response was "CI+." Since this mistake appeared to be quite common, the lesson was modified to give a student who answered "Cl+," a specific comment reminding him that when an atom gains an electron i t forms a negative ion. Another common error was to omit the suverscriot or the caoital "C;" in the revised version students who typed the sy&bol incorredlv were reminded that the c a d t d (or suuerscriut,t)was necessary. In addition to storing specific incorrect responses, statistical data on the interactio;oi'a large number of students with the lesson are automatically collected. PLATO records the number of questions each student was asked, the number which he answered correctly on the first try, the number of errors he made which were specifically anticipated hy the author and the number of unanticipated errors, the number of times the student asked for help, and the time spent by the student, for each logical segment or "area" of a lesson. Given such statistical information. it is oossible to develon a profile of a lesson indicating which areas of the lesson are particularly difficult or especially easy for students. Such a profile often points out the need for revision of a particular lesson segment, in order to make the formulation of a problem
-
746 1 Journal of Chemical Education
Figure 3. Histogram showing the average number of questions answered by students in each section of a lesson on alkene chemistry. Area 8 contains a review problem set
Figure 4. Histogram showing the distribution of the number of probiems worked in area 8 of the lesson an alkene chemistry. The problems are presented in randm7 order and are removed from the list if the student answers correctly on the first try.
clearer, to provide more help, or to give the student more background before asking him to work problems. Figure 3 shows the average number of questions encountered in each area of a lesson on alkene chemistry (12) by the 174 students for whom data were collected. T h e short drills in area.: 1,5, and 6 stand out, as does the review problem set in area 8. The questions in the other areas were not practice problems, hut usually leading questions about the mechanism of a particular reaction. ~ l t h o u g hthere were many more questions asked in the practice problem set in area 8 than in anv other area. this nroblem set did not take sienificantlv " longer to complete than did the other areas. Looking in more detail a t the final orohlem set. Fieure 4 is a histoeram showine the distribution df the numbkr of problems wo:ked in area 8 for the entire class. In this area oroblems were oresented to a student in random order. If he got a problem correct on his first trv, it was removed from the oroblem nool-if not he was given t h e problem again later..^^ orde; to complete the uroblem set a student had to answer each of the 24 different problems correctly. As the histogram indicates, the number of questions in the problem set thus varied considerably from student to student. The scatter plot in Figure 5 illustrates the functioning of this drill algorithm-the more errors a student made, the more questionshe had to answer. The difficulty of
