An Approach for Large-Enrollment Chemistry Courses Melanie M. Cooper Clemson University, Clernson, SC 29634 One of the major goals of most chemistry instructors is to encourage their students to think and to apply the concepts that they learn. Although students may be able to reproduce specific types of calculations they have seen before, many are unable to apply their knowledge to new situations. In large enrollment courses where little, if any, personal interaction may occur between instructor and students, this problem may well go unnoticed until the first exam, where the student may be bewildered by questions that require application of knowledge. One solution to this problem is the use of writing assignments. Carefully crafted writing assienments allow students to reflect upon the materia1;and the reflection process provides a clearer understandine of the subiect matter. Writine about chemistry actively involves the student in the learning process-a prerequisite to a successful completion of the course. Writine in chemistrv courses usuallv has been associated witc formalized l h r a t o r y reports", term papers, and research proposals. However, the use of other types of writine assienments in chemistrv courses. usnallv in coniunction with such movements a s writing across the curriculum (1)and critical thinking (24),recently has gained increased prominence. These less formal writing experiences, in which the student is writing to learn, to organize, and to understand material are vitalprerequisites more formal writine tasks. Manv students omit such exercises and fail to resize that they are essential for the successful study of a subject. The fact that a n average introductory chemistry course a t Clemson Universily has around 200 students per section precludes many i f the more traditional writing assienments simolv bv weieht of numbers. Most teachers of large enrollment courses probably would not have the time or G h a t i o n to read and grade200 essays several times oer semester. and manv would not feel oualified or able to give such a large number of essays the proper attention. Therefore, the format chosen for the assignments given to our eeneral chemistm students was that of note writine-a sho; (100-200 word, informal summary or description of the topic assigned. The short length of the note allows the teacher to read them fairly quickly, and the note format is useful to the students, because these future professional scientists and engineers often will be required to communicate their ideas. in the form of a note or memorandum. The use of writing assignments, such as those described below, supplements other teaching and learning tools used in our Clemson chemistry courses and leads, we hope, to an increased understanding of the concepts to be learned.
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Examples of Assignments Examples of the different types of assignments and student responses are given below. The following is a pair of assignments that usually are given two or three lectures before a major test.
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Homework on Unanswered Questions
Homework Assignment I Choose one topic that we have covered in class that you feel you do not understand. In about 150 words (1page) summarize what it is that you do not understand or the pmhlem that you are experiencing. Note the following points. 1. Be specific about key points 2. Try to avoid blanket statements such as "I don't under-
stand anything." 3. Think about whether you muld give an answer to your own question. Do not pose unanswerable problems.
Bring two typed or clearly written copies to the next class. Homework Assignment ZI Exchange the homeworkasiignment due today with a neighbor. You will then have a question or statement about a principle that your neighbor does not understand. Your assignment is to try to explain the principle troubling your neighbor. Aeain this assirmment should he brief and concise. Annmdma& 10&200 Lords should be suflirient. lbrn in yo& answer at the begmningoF the next class, stapled to the question you received. You also should bring a copy of your answer for your neighbor. We have found i t important to give these rather detailed instructions. otherwise the students are not exactly sure of the requirements. In addition, students are given examples of papers that are felt to have been of help by copying &pprop&& examples onto overhead transparencies that the instructor reads to the classes. For completion of this pair of assignments, the students are given credit equal to a n "in class" quiz. Such a quiz would normally comprise less than 1% of the total grade and is negligible for most purposes. The student is given credit solely for completion of the exercise. No attempts are made to grade for content, spelling, or grammar. If an incorrect answer is given to another student the writer is asked to rectify the matter. Typical Set of Responses
The following question and answer pair deals with the t o ~ i cof limitine reaeents that students freauentlv find cokusing. The answer gives a succinct easy method for determination of the limitine - r e a-g e n h n e that the author now shares with the students. rNok: student exercises have been retyped for publication here, but spelling and gramma; have n & been changed.)
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Problem Limiting reagent problems confuse me. I have trouble distinguishing what the actual limitingreagentis. Is it the one that is entirely used up or the other? The math is not that difficult. My problem comes in the middle of the math aRer I find the actual moles. Once I finish the mole ratio part I find it hard to decide which is the limiting reagent. Answer The limiting reagent is the chemical that is completely used up. I fmd that the method Dr. Cooper uses on the board is too
confusing. I find a better to divide the number of molesofeach compound by its coefficient. The smallest resultrng number is tbat of the limiting reagent. There are several benefits to this kind of exercise, one of which is that a path of communication is opened between the teacher and-students. manv of whom mieht not otherwise seek help or feedbaik on their p r o g r e s ~Because the assienments are received bv the teacher several davs before; test, it is possible to review the major problemareas in help sessions or in class. Using this system, feedback may be obtained on the areas in which students have the most nroblems. In some cases this information mav allow the i & w c t o r to change the approach or explanation, or spend more time on specific problem areas. Perhaps the most important benefit is that of simply makine the students sit down and think about the material coiered. I n addition, i t forces the students to try to organize the material in their minds well before the test. The process of thinking about the material they do not understand and even learniw that they do not, in fact, understand it can be a major breakthrough f& somestudents. Students have commented on this organizational process, and the help they have derived from these assignments. A third area in which these assignments are h e l p l l is the r e ~ l vDmcess in which the student has to answer the question of a neighbor. The proeess of explaining a concept to someone else is oRen very useful in the clarification of ones own understanding of
