Critical-Thinking Writing Assignments in General Chemistry N a d a VanOnkn Sacramento City College, Sacramento, CA 95822 Educators and emdovers . . are both concerned that our science students are unahle to communicate their knowledge. Educators have found that continuing sciencestudents gradually lose their freshman writing skills. Employers complain that science graduates are technically competent, but they cannot communicnte; the graduates are able to make reams of calculations, hut thev cannot explain the purpore for, or significance of, those calculations. This prohlem was emphasized at the recent national American Chemical Society meeting in Chicago.' In a symposium sponsored by the Division of Chemical Education, i t was concluded that chemistry students lack communication skills, and that the prohlem must be solved by chemistry departments, not English departments. However, learning chemical writing is very similar to learnine chemical calculations: in both cases, the basic skills are tau& in other departments, but the application of these skills must be provided in the chemistry course. Just as we cannot expect-students to learn chemical calculations by solving one veni com~licated~ r o b l e mso , we cannot expect s t u d e k to lea& chemical writing by composing one term r e ~ o r tBoth . writing and calculations require much practice inkach segment of the course. T o motivate chemistry students t o practice writing skills, we must convince them that chemical writing is important. Students are convinced that chemical math problems are important because much of their course grade is based upon their ahilitv to solve such problems. They will also think chemical writine is important if part of their made is based . upon writing assignments. But. to be of real value, the writing-assignments must be . more than the usual end-of-chapter questions, which can be answered by copying the appropriate sentences from the chapter. Instead, the writing assignments must require a synthesis of the concept fragments taught in the chapter. In addition, just as we find that chemical calculations are more meaningful to students if they are related to the real world, so are chemical writing assignments more valuable if they illustrate real-life problems.
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Chem. Eng. News 1985, 63(38).32.
506
Journal of Chemical Education
Descrlptlon For some years I have been searching for brief chemistry writine- assienments that the students will consider to be an - " important part of the course; a t last I have found a type that seems effectwe. These assignments are alwavs related to the text concepts being studiei, and many of thdm are examples of practical applications of chemical concepts. T o complete the assignments, the students must first solve a chemical prohlem, then they must explain, discuss, or apply their results. Three examples of writing assignments, which are given as part of the homework for ionic equilibria, are shown in Appendix 1. I have four goals that I want to accomplish with the writing assignments: (1) to encourage students to think about the chemical concepts, (2) to find out if the students understand the chemical concepts, (3) to show students that chemical concepts can be-very practical, and (4) to help students improve their written communication in chemistry. I believe that writing is an effective means for improving thinking skills, because a person must mentally process ideas in order to write an explanation. Writing also improves self-esteem because mentally processed ideas then belong to the writer. and not iust to the teacher or textbook author. Many of my writing assignments require four thinking steps: (1) decide what information is needed to solve the problem, (2) find the necessary information, (3) use the information to solve the ~ r o h l e mand , (4) bstify the choice of information used for solving the problem. For example, in question 2 of Appendix 1 the students must first realize that they need K,, tables and solubility rules: next, thev must use the rules and tables t o select particular reage& for the separation; then, they must make calculations to show that their particular separation is acceptable; and last, they must explain their reason for selecting the particular reagents. In addition to giving students thinking practice, writing assignments also reveal student misconceptions. For example, "In the electrolysis, electrons were pulled away from Mg2+, and then Mg was plated out on the Mg anode." Or, "Excess NaOH causes zinc hydroxide to dissociate into Zn2+ and OH-." Although I do not attempt to teach English grammar, on their papers I do note construction errors, such as sentences
that are short and choppy, ambiguous, or awkward. For example, sentences such as the following are marked: "To the zinc hydroxide I would add HCl to form zinc hydroxide complex and a weak acid to ionize zinc." Or. "In order to separate the copper from zinc and lead, the formation of the cooper complex ion. a roval blue solution, can be done bv a d d h g conckntrated ammonia." Or. . . ~ o t h i nwill ~ appear tb happen at first. We are dri\,ing out HNO? as SO3 as." After each writing assign&nt is turned in;f post t h e chemical solutions and some acceptahle student responses. (Students enjoy-reading what their peers have written.) If none of the student responses is acceptahle, I re-state the question and ask the students to rewrite their responses. At present, this is all the writing instruction that I give to students. Heln is available in the English writine lab. hut until I began grading writing assignmtks, students did not take the time to get assistance because they did not consider writing to be important in chemistry. But now, by the third or fourth assignment, they realize that how they write really does matter. Since most of my students are very serious and competitive, their writing quickly improves, and many students become quite creative. For example, a student response to a huffer writing assignment is given in Appendix 2.
Evaluation These writing assignments accomplish very well the first three goals given above. Especially, the assignments do cause the students to think about the chemical concents and do help students relate t h e concepts t o t h e real world: (However, manv of the students are still in need of assistance with the merhanicsof sentence construction: we hope to solve this ~ r o h l e mi~ventahlishinradrop-in writing lab iust for science The assignments have also provided an unexpected honus-that of improving students' social skills. Because the problems are so challenging, the students find it necessary to get rogether in groups to discuss the cuncepts and prohlem solutions. There in much discussion and arguing, and sometimes whole groups will come to me to find out which person is on the right track. Then, after the members of the group have decided how to solve the nroblem. each member must understand the solution well enough towrite his or her own ex~lanation.iustification. or annlication. (If thev CODV from each other, &at becomes'imm&ately oh;ious; ihe;¬ find answers in any textbook, and they cannot copy from previous students because I change the questions each semester.) The only drawback I have found to these assignments is the time required for grading. I ameliorate this problem to some extent by limiting the writing portion to less than one page and by requiring writing assignments only every other week. Also, although I note construction errors, I grade the writing holistically-does i t make sense on the first reading? At the beginning of asemester, the students complain that the assignments require too much time and also that "this is a chemistry class, not an English class."But by the middle of the semester, they are willing to concede that the assignments are valuable. The evaluation by the students are summarized in two student comments shown in Appendix 3. Perhans the best evaluation of all is that. near the end of the semester, students bring me questions fbr future writing assienments. Thev have caueht some of t h e vision of what education is trying to accomplish.
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Appendlx 1. Examples of Wrltlng Assignments for lonlc Equlllbrla Example 1. Solubility Equilibrium-Qualitative You have been given an ore that consists of sulfides of capper, lead, and zinc, embedded in quartz (SiOl). (1) Explain-with words
and net ionic equations-how you will separate the three cations, and then identify each one. (2) Explain why youselected the partieular separation method.
Example 2. Solubilltv . Eouilibrium-Quantitative . You are a chemist workine for Salt Flats Maenesium Comoanv. You are testing a salt sample"that contains 40%&CI, 25% KC^, 15% CaC12,10%MgCI2, and 10%sand. (1) Describe, using a flow chart, a good method for the separationof magnesium from this mixture. (2) Assume a certem quantity of the mixture, then calculate the amount of each reagent that you will use to separate out at least 99%of the magnesium. (3) Write a memo to your supervisor explaining why you have selected the particular reagents for recovering the magnesium. Example 3. Competitive Equilibria You are a chemist working for the Monterrey Manganese Company. You have been given some ocean nodules that contain 40% manganese sulfide, 30%zinc sulfide, and 30%copper sulfide. You are assigned to work out a process for recovering the Mn from the nodules. Select a method which requires the use of one or more buffer solutions. (2) Describe the method with a flow chart. (3) Calculate the composition of your huffer. (4) Make calculations to show that your huffer(s) willmake thedesiredseparations. (5) Write a memo to your supervisor explaining your method and reasons for selecting the particular buffer. Appendix 2. A Buffer Wrltlng Assignment You are the manager of River City Pet Store. A customer is very distraught because the fish m her backyard fish pond are dying. Whennhe brineavou a sarnole of the water. vou fmd o u ~ that thc oH of the water i s i i , but thisspecies of fish'lhes best in water of ;H 6.8. (1) Select a good buffer system for a fish pond. (2) Calculate the quantities of buffer componentsthat should he added to the pond to maintain the pH at 6.8. (3) Write aletter to the customer telling her how to treat her fish pond. (Make sure the huffer chemicals do not kill the fish.) One student selected the dihydrogen phosphate-monohydrogen phosphate buffer system and calculated the mole ratio necessary for a buffer of pH 6.8. Then she calculated the quantity of buffer componentsnecessary tomaintain the pH of five gallons of the pond water constant at pH 6.8. The student next "prepared" a product containingenough huffer for 1000 gallons of pond water. She "marketed" this product under the trade name, "Aqua-lock". The letter she wrote to her customer is as follows: Dear Mrs. Frame: The completed analysis of your pond water indicates that a pH adjustment is needed to provide an adequate environment for your fish. Fortunately, this problem can be easily corrected with one of our products, Aqua-lock, pH 6.8. Aqua-lock is available in one-gallonjugs for only $25.95. I recommend that 5.5 quarts of the product be used immediately on your pond and once a month thereafter. Periodic maintenance thereafter could be cut down if you measure your pH and add the product only when the pH changes. Accordingly, I also recommend that you purchase Wardleys' Jr. pH Kit (instructionsincluded) for only $14.98. River City is committed to customer service. If we can be of further help, please feel free to call on us at any time. Sincerely, Valerie Ayala, Manager
Appendix 3. Student Evaluatlons of ~ r l t l n g Assignments "Writing assignments have helped me in understanding chemical concepts by requiring me to apply tho= concepts to practical problems. These assignments have made me realize that chemistry does in fact continue beyond college." Alan Chan "The writing assignments have comhined different small questions into larger questions which have forced me to sit down and put together the knowledge I have gained in a synthesized way. The writing assignments have been useful in allowing the students to come up with their own answers to questions, which is like being out in the real world, where there isn't always an answer worked out for you already." Nancy Goyings
Volume 64
Number 6
June 1987
507
