R. N. Reusch and P. H. Carnell
Albion College Albion, Michigan
An Experimental Program On Chemical Equilibrium
Teachers of freshman chemistry today find it increasingly difficultto sat,isfy the varying needs of studcnt,~,whose previous experiences range from excellent high school chemistry courses to no training at, all. In addition, the rapidly increasing student population and the resulting large classes essen'tially exclude all forms of teacher-student interaction other than formal lectures. Assigned readings and films help to buttress the lecture material, but must also he regarded as passive methods of learning, whose inefficiency is demonstrat,ed by t,he poor performance of many students. Since programed instruction requires the active participation of the student in the learning process, it can be used to alleviate these problems. Since each student can work a t his own rate, repeating scctions if necessary, it ran accommodate a wide range of abilit,ies. The program reduces the differences between students by bringing all of them up to a minimum standard. With the tedious and t,ime-consumil~gdrill work accomplished for him by the program, the teacher can use the lecture t,o build on this fundamental knowledge and discuss more advanced topics according t,o his o m int,erests and those of his st,udents. Our program on "Molecular Equilibrium," now in its final testing edition, is the first of a series which will cover the subject matter of general college chemistry. Equilibrium mas chosen as the first topic because most students find it difficult, and it therefore offers a challenge to the programer and presents an excellent opport.unit,yto develop good programing technique. Organization of the Program
The program is arranged in t,hree parts: (1) the law of chemical equilibrium, (2) equilibrium changes, and (3) equilihrium calculat,ions. Each part consist,^ of many small sect,ionswhose t,itles correspond roughly t,o paragraph headings in a textbook; in the part on equilibrium calculations, each problem is a separate sect,ion. This arrangement makes it easy for the tcacher to view the content of the program and adapt it to his needs. I t also helps the st,udent to locate specifir topics for study or review. The program is designed so that. over SOYo of t,he student,~mill answer a given frame correctly. If a student's answer is wrong, he will only have to review a few frames to find his error, for the logical sequence of steps will not allow him to progress very far witahout comprehension. A series of three typical frames in the program are presented in Figure 1.
Testing the Program
In order for the program to be effective, the size of the steps taken by the student in moving from one frame to the next should be fairly uniform. Moreover, the steps should be neither so large as to produce a high probability of error and t,hus discourage t,he student, nor so small as to unnecessarily lengthen the program and increase the time required to complete it. In testing a program, the percentage error for any given frame can be taken as a measure of t,he step-size for that frame. Before testing the program on a large scale to determine the step-size, it was reviewed by a few interested students at Albion College to detect major errors and inconsistencies. Even one or two students can indicat,e which frames need t,o be reworded, and which areas of the program are vague or misleading. The program was revised and then tested on a group of approximately 300 freshman chemistry students a t Michigan State University who had received no previous lectures on equilibrium. From the completed programs, the percentage error for each frame mas determined. Since the optimum percentage error for
A.
The reversible reaction
+
+
+
Acoi Bw, 0 Cw Dw, A is allowed to reach equilibrium. If the temperature is increased, i.e., heat is (removed, added), Le Chatelier's Principle states that the system must adjust to heat. A.
+
+
+
B. evolved absorbed
-
+
-
+
C. To relieve the stress of an increase
in temperature on the reversible reaction: A(,, BI,, e Cm Dl,, A heat must be Therefore, it is the (fonvard, reverse) reaction which is favored. The formation of (reactants, products) is favored.
+
C.
+
B. When the fonvard exothermic reaction occurs: A(,, BI,, CI,, Dc,) A heat 1s (absorbed, evolved). When the reverse endothermic reaction ocAm curs: CW) DW A B,,, beat is (absorbed, evolved).
added absorb
+
+
absorbed reverse reactants
Presented at the Symposium an Programed Instruction st the 124th Meeting of tho American Chemical Society, Atlantic City, New .Jersey,September, 1962. Volume 40, Number I , January 1963
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27
frames in programed instruction has not yet been estahlished, it was arbitrarily set a t 5-20y0 for this program. All frames with percentage errors outside this range were reviewed. Frames with over 20% error were reworded or replaced by two or more frames to decrease the step-size. Some frames with percentage errors less than 5% are unavoidable, but when several of these appeared in a row, the step-size was increased by eliminating some frames. Evaluation of the Program
The only criterion by which the worth of a program can be judged is its success in teaching the student. Unfortunately, time and circumstances did not permit us to administer a post-test to evaluate the effectiveness of this program. We felt, however, that it would be useful to obtain the student's opinion as to the value of the program. See Table 1. There was surprisingly little variation in the evaluation of the program by students of different abilities. Their reactions were uniformly favorable: 80% or more of the students in each group felt the program was effective. The high percentage of "A" students who approved of the program was particularly gratifying, since we had expected opposition from this group. By far the greatest objection to the use of the program was the time required to complete it. The amount of time reported ranged from 3 to 12 hours, averaged about 6 hours. The present edition of the program is somewhat shorter, and it is expected that additional testing will abridge it further. The students were particularly critical of errors in the program. Most of the errors were typographical,
28
/
Journal o f Chemical Education
but their presence is a legitimate cause for complaint. Errors are far more serious in a program than in a conventional textbook. For a program to be effective, it, must be absolutely reliable, since even one wrong answer can disrupt an entire sequence and cause confusion. As expected, a few of the students objected to learning by programed instruction. These students should be offered textbook references which cover the same material as the programed assignments. Certainly, programed instruction is not the only method of learning, and not necrssarily the best one for all students. It is believed, however, to he a n effective teaching aid, arid an excellent method for the great majority of students to obtain a strong foundation in the subject. Table 1 .
Evaluation by Students
% of % of students students 61yq glvlng Grade in ~ o s t w e ~oeitive previous &smer to answer to chemistry Numher of question question course atdents IAi* (Ria Son-repeating students
A B C
Total nonre~eatina &dentsRepeating students Total students
D
22 80 $13 15 210
86 80 82 80
82
90 i0 80 100 85
a Question A: Do vou fccl that the Dropram was sueeessful in teaching you thp principles of equilibrhm7
question B: Wndd you voluntarily use other programs in gcncral chemistry if they acre available?
