Is Writing an Effective Way To Learn Chemical Concepts? Classroom-Based Research Naola VanOrden Sacramento Clty College, Sacramento, CA 95822 We educators want our students to "learn" chemistry, hut most of us want the students to he able to do more than recogni7e or recall information. We would like the students to he able to (1) inteerate concepts. (2)apply the i n t e ~ a t e d concepts to real lifer and (3) c ~ m k u n i c a i e t h o s eco&epts. However.. d e s.~ i t eour desires, students tend to learn what is necessary to complete the homework and pass the exams. If we want students t o integrate, apply, and communicate chemical concepts, we must give them practice and test them on those skills. Several years ago, when I found that students could not perform well on exams that required an integration and application of chemistry concepts, I devised "critical-thinking writing assignments"' to give the students practice in simulated real-life chemistry and practice in communicating chemical information. Even though this type of assignment requires much more thought and effort than the traditional end-of-chapter exercises, student response t o the assignments has generally been favorable. However, after requiring writing assignments for several semesters, I wondered if they were really worth the time and e f f o r h n the part of both students and instructors-that they required. .
This study has attempted to show whether or not criticalthinking writing assignments are more effective than traditional end-of-chanter exercise assienments in ~romotingunderstanding of chemical concepts.- he study included 21of the students reeistered for the second semester (Chemistry 1B) of a traditional two-semester general chemistry course. A comorehensive midterm exam, which required application of m&y concepts to a real-world problem,kas chosen as the orimarv measuring instrument. An attitude survey was seiected as a secondary measuring inatrument. Allstudents were given the same lectures and performed the same lahoratory experiments. In addition, for the 8-week study, the class was divided into two groups on the basis of laboratory enrollment. After the 8-week period, both groups of students were given the same homework assignments, which included end-&chapter exercises and writing assignments. During the project period, the control group (A) was assigned weekly end-of-chapter exercises, while the experimental group (B) was given critical-thinking writing assignments. For example, one of the control-group questions was: "The equilibrium constant, Kc, for the reaction PCldg) = PC13(g) Cla(g) is 0.0211 a t 150 O C . Calculate the equilihrium constants of PC15, PC13, and Clz starting with a concentration of PC15 of 1.0 M." An experimental-group question on the same subject was:
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Onecause of acid rainis the reaction SOdg) + HzO(l) = HzSO4.
The SO3is produced by the oxidation of SO?,which is a common
' VanOrden, Naola. J. Chem. Educ. 1987,64,506-507.
byproduct of the manufacture of many metals as well as the burning of sulfur-containing fuels. One method for utilizing the waste SO? is to oxidize it to SO1 and then oass the eas throueh powderrd, solid CaO, according 10 thr equa;ion SO i g +~ C~O;;) = C a J O d . The CaSO' is sold for fertilizer. Assume, for this prublprn, that you are a chemist workin8 frr Acme Mines and Minerals Company. (A) Calculate the maximum number of moles of CaSOd that can he produced (in a closed container) from 0.25 molL SO8and excess CaO at 150 *C.Kc = 8.2. (B) Explain why 0.25 mol of SO8 and exCaO will not produce 0.25 mol of CaSO4 at 150 'C. (C) Write a Letter to your plant supervisor in which you (1) explain the calculations of (B), (2) state what conditions you would change in order to produce a greater amount of CaSO,, and (3) explain why you think your suggested conditions would praduee a greater yield.
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Only a portion of each homework assignment was graded, and each group was given a weekly quiz that had questions similar to those found on the homework. The instructor discussed the homework with each respective group after the homework was turned in and hefore the auiz was eiven. Althoughit was not possible to ensure that the c ~ n t r o l a n d experimental group students had equal ability, the initial average chemistry 1A grade (the single parameter that we have found best predicts student success in chem 1B)was comparable for hothgroups a t the beginning of the semester. During the last quiz period, students in hothgroups completed an attitude survey and then made comments about their homework and quizzes. At the end of 8 weeks, all students were given a 3-h openbook examination containing material unfamiliar to both mouns. The exam consisted of a steo-bv-steo " . . . descriotinn of two industrial methods for producing elemental cobalt, followed hv auestions about the methods. The exam auestions k the appendix. are Since there were some essav auestions on the exam, student papers were marked with code numbers, so that, when madine the -Daoers, the instructor did not know the identity of the author df an; of the exams. After the exams were graded, the students were allowed to look at, hut not take, their papers. An optional 1%-h makeup exam, which was similar in format t o the midterm exam, was given 2 days after the students were informed about their performance on the first midterm. ~
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Results The students in the exoerimental erouD were extremelv frustrated a t the heginni'ng of the project. Although the; were given detailed samples, and instructions for the writing assignments, their performance a t the beginning of the proiect was unsatisfactorv. However, each week the students were given repeated i&uctions about selecting the pertinent concepts, using those concepts to make calculations, and then explaining the results of their calculations in a logical manner. Each week, the best homework papers were Volume 67
Number 7 Julv 1990
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Table 1. Comparison ol Homework, Quiz, and Mldterm Scores Recelved by Control-Group and Experimental-Group Students Work Tvoe
ConbDl
Exmrimemal
Is
n Homework
18 89.6 10.9 57.5 21.0 29.9 17.4 41.8 24.2
24 86.1 10.2 68.7 13.5 48.9 23.9 64.6 17.2
-1.05 1.98 2.99 3.06
Quiz Midterm I Midterm I1
Statistical Conclusions: 1. NOsignificant difference in homework scores. 2. Significant difference In bmh quiz and midterm scores. *Test statistic from normal probabiiily diahibution comparing means of independent sample5 tom two populations.
Table 2. Mldterm and Make-up Mldterm Score8 ot Siudents Ranked According to Grade Recelved In Chem 1A " A Students Midterm Make-up control Omup n 4 Mean 51.0 SMDev
14.6
4 73.5 7.4
n
6 69.8
3 92.7
Mean
"B" Students Midterm Make-up
"C" Students Midterm Make-up
2 43.0 19.8
2 52.0 25.5
12 20.7 9.5
9 25.4 9.8
7 46.0
6 62.0
11 39.5
9 55.8
1 No 61gnillcanldlfferenCeOntlmt m d t m bstween grmps tor A studem. s~gmt~canf d nsrencs on makeup modterm 2 Very slgn~llcanl difference on o m m~dlsrmexamabetweengroups fa' C" students.
posted for the other students to read. Each week the students' performance improved. The midterm exam was a disaster for many of the students. Although all of them had performed similar calculations in their homework and quizzes, many of the students spent much of the exam time trying to decide what calculations they were supposed to make. Almost all students performed hetter on the makeun midterm exam. A statistical analysis was made to determine if the scores on the homework, quizzes, and midterms were significantly different between the two groups. The results are given in Tahle 1. Because the experimental group, a t the end of the project, contained students with a higher average chemistry 1A grade, an analysis was made of midterm grades for "A", "B", and "C" students from each group. Tahle 2 shows the results. A statistical analysis of the attitude-survey instrument showed that asignificantly greater number ofstudents in the experimental group felt that the homework was really challenging and that the homework questions required a very eood understandine of chemical conceocs. Both e r o u ~ sfelt that the amount 2 work required fo; the homewo;k was about right for a 5-unit science course and that their homework taught them knowledge and skills that would he helpful to them in later courses and in their career. The comments made by the students on the survey instrument indicated that most students in bothgroups were satisfied with their homework. One student i n t h e experimental group felt the type of homework and quizzes made the class more difficult than normal. One student in the control group complained, "Group B, even if they didn't perform as well on the ouizzes. have eotten a better understandine of the concepts behlnd the work. It'seasy to memorize an equation and kickout numbers, but a more thorough understanding ofthe
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584
Journal of Chemical Education
work makes life a lot simpler in the long run, especially in other courses." Most of the students in the experimental group commented that thev felt this t w e of homework and auizzes would be of value tothem in laic; courses, that they liked the real-life aspect of the questions, and that the homework was a lot mbre interesting than traditional end-of-chapter exercises. Onestudent commented: "What I likedabout the homework and quizzes was that it wasn't just a lot of calculations and busy, tedious work to get an answer. We had to know why we used the formulas and how it applied, which gives one a much hetter understanding of things, rather than plugging numbers into formulas." This study produced some surprises. One was the very few complaints from the experimental eroun students that their homework was more diificult. In fact, several students commented that they knew they had to work much harder, hut they felt they were learning more and so they wanted to continue the experiment. Also unexpected were the complaints from thi better students in the control group, that they did not get to learn as much as did the students in the experimentalgroup. The difference between quiz scores of the two moups was surprising to the instructor. Since the c o ~ t r o l - home~~u~ work was much easier than that of the experimental group and the quiz questions were almost identical to the homework questions, it was expected that the control group quiz scores would be higher than that of the experimental group. Instead the reverse was true. A possible reason for the unexpected difference, with implications for chemistry instructors, is that very little information is actually learned from working drill exercises with an open book. Conversely, if a student puts forth the mental effort to integrate concepts to make calculations and then explain the significance of those calculations, real learning does take place. Some of the results of the quantitative portion of the attitude survey were inconsistent. For example, the author received complaints from nearly every student in the experimental group that the homework required too much time, hut most students from both mourn indicated that the amount of work required for thehomework was about right for a 5-unit science course. And although very few students from the control group made any written or oral comments about the usefulness of their homework, most students in both groups marked that they agreed that the knowledge and skills learned in the class would be helpful later on. I t may he that the students were marking the responses that they thought the instructor wanted them to mark. The instructor expected a better nerformance from the experimental-group student on the first midterm exam. But, it is ~ r o h a h l vtoo much to exnect students to learn. in onlv 8weeks, how t o cope with multiconcept, application-type questions. Also, the exam would have been a more valid instrument if it could have been a take-home exam. However, even under the stress of a time exam. the differences between the control and experimental group were significant to almost 3 standard deviations. This result indicates that students can be taught to apply chemical concepts to simulated real-life problems, as well as tounderstand and explain the significance of the results of their calculations. A comparison of the exam scores for "A", "B", and "C" hestudents indicated the followine: (1) ~ ~ ~ .. . . that the difference tween the scores of the "A" students was not significant on the first midterm. but it was on the make-up exam., (2) . , there were too few "B'; students in the control k o u p to make a comparison. and (3) the "C"students in the exnerimental group performed significantly better on both exams than did the "C" students in the control erouo. This last result leads to perhaps the most important conciusion from this study,
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i.e., ordinary, average students can be taught higher orders of learning skills. Summary The performance of the experimental group indicated that the completion of frequent critical-thinking writing assignments is a more effective way to learn chemical c o n c e ~ t s thHn traditional drill-type exercises. Acknowledgment T h e author expresses appreciation to Gene Sellers, of the Sacramento City College Math Department, for making the statistical analysis of the data from this study. This project was supported in part by Sacramento City College Staff Development funds. Appendix: Mldterm Exam Questions 1. Draw flowcharts for each separation method. 2. Step (la). Explain why Co and Fe dissolve in sulfuric acid but
Cu does not. (Assume standard conditions.) Justify with equations and calculations. 3. Step (lh). Calculate the pH of the solution after NasCOs is added. 4. Step (lc). Explain why is it necessary to add an oxidizingagent to the cation mixture before separating the ions by hydroxide precipitation? Justify with equations and calculations. 5. Step (Ic). Explain why the solution was made basic before the oxidizing agent was added. Justify with equations and calculations (Assume standard conditions.) 6. Step (Id). What buffer would he good to separate the two hydroxides? Justify with equations and calculations. 7. Sten . (2hL . . What must he the initial voltaee .. ranee to reduce the copper, hut not the cobalt, a~sumingstandard conditions? 8. Steps (If and 2 d ~Cmnparr . rhe enerRy (work),in kJ/mol of reactant, required for the final reduction rtrp of each method, using the given conditions. 9. On the basis of the information given in the question and the results of your calculations, explain which is the most economical method for producing cobalt? Givespecificreasons for your condusions.
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Number 7
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