In the Classroom
curricular change digests
Getting Real: A General Chemistry Laboratory Program Focusing on “Real World” Substances Robert C. Kerber and Mohammad J. Akhtar Department of Chemistry, State University of New York at Stony Brook, Long Island, NY 11794-3400
In order to confront the abstractness of the freshman chemistry syllabus and the consequent failure of students to relate what they learn to their everyday lives, we have designed a new freshman laboratory program. It is intended as an interface between the substances that surround the students in their ordinary lives and the abstract principles presented in chemistry classrooms (1). A laboratory should provide the organized experiences and observations that underlie the intellectual constructs of chemistry, and tying these experiences and observations to the real world can help to provide motivation for study of the principles. The freshman laboratory program constitutes the foundation for subsequent laboratory courses. However, the good habits we strive to develop there (careful observation, thorough record keeping, proper use of equipment, objective data analysis) are essential to all scientific work, and are intended to provide lasting educational value for all students, especially those who do not take later laboratory work. What We Do A list of the laboratory exercises carried out during 1994–1995 is presented in Table 1. The course incorporates the following features. 1. The exercises deal with recognizable, everyday substances, not just with “chemicals”. That “baking soda” and “sodium bicarbonate” are the same is a chemical truism of which the students may be aware, but the visible presence of the Arm and Hammer box nevertheless helps them to make connections to the world outside the laboratory. Perceiving the connections, students may be inspired by curiosity to understand chemical phenomena better, not just to tolerate what they are being taught, as an irrelevant hurdle in the pursuit of a career. 2. Since many significant substances around students in the everyday world are organic, we work in the lab with organic as well as the usual inorganic materials. These include analgesics, vitamins, antifreeze, foodstuffs, dyestuffs, plastics, and fibers. In working with these materials, we present chemical structures wherever possible, but do not emphasize organic nomenclature or functional group chemistry beyond identifying, as appropriate, acidic and basic groups and other key structural features. 3. As can be appreciated from Table 1, the course organization is overtly based on the nature of the materials themselves—household “chemicals”, food and beverages, pills, and plastics—rather than on abstract chemical principles. Organizing the course on the basis of the materials studied emphasizes their relevance to students and focuses interest on the actual results obtained by the individual students. Nevertheless, a coher-
ent sequence of development of laboratory techniques and gradually increasing opportunity for less tightly directed student experiences is maintained. Laboratory exercises cover most of the usual topics, including stoichiometry, qualitative analysis, quantitative analyses by acid–base and redox titrations, and colorimetry. We have not, however, found or devised exercises dealing with thermochemistry or electrochemistry; readers’ suggestions in these areas would be welcome. 4. The instruments, equipment, and techniques used in the laboratory initially were the same as previously used, so that we have been able to introduce this program without initial capital expenditure. The exercises rely substantially upon mass measurements and titrations, with pH meters and colorimeters brought into use as the year progresses. We are now in the process of introducing Fourier transform infrared (FTIR) methods into the laboratories. This will add a very powerful tool to the students’ repertoire. Its use will greatly expand the opportunities for directed-inquiry investigations of real-world samples in the context of the course. 5. Some of the exercises in Table 1 will be recognized by readers of this Journal as standard ones, found in many lab manuals or available as commercial modules (2). To provide a comprehensive focus on “real world” substances, however, we have also devised some new laboratory exercises or adapted existing ones. Sources are cited in Table 1 and in the references; in most cases, published exercises have been extended and modified to fit our theme. Some general descriptions of the more novel exercises appear below. We will be pleased to provide details on any of the exercises to interested readers. 6. To further emphasize the quotidian nature of the samples under study, we have encouraged students to bring their own samples to the laboratory by offering a small number of bonus points (up to 5% of the total points awarded in the course). Student participation has been very gratifying, with two-thirds of the students, on average, bringing in designated materials (indicated in Table 1). Although our primary purpose in encouraging “bring your own” is pedagogical, we are not unaware of a favorable effect on the course budget. 7. Fill-in-the-blank report forms are used to guide calculations in the quantitative exercises, helping to assure reliable conversion of measurements into meaningful results that allow comparison of various student samples. In the more qualitative exercises, however, we emphasize use of the laboratory notebook for recordkeeping (3). As an incentive for development of good notebook habits, students are allowed to use their laboratory notebooks on lab quizzes, and the notebooks themselves are graded for thoroughness and accuracy at least once each semester. 8. Most laboratory exercises are conducted on an S/U
Vol. 73 No. 11 November 1996 • Journal of Chemical Education
1023
In the Classroom
basis. Numerically graded exercises, indicated in Table 1, are performed only after students have gained experience in basic operations by working on S/U exercises. Table 1. Sequence of Laboratory Exercises
Some Features of the More Novel Exercises 1. In “Identification of Household ‘Chemicals’ ”, each student is given a white powder and a list of some twenty such powders that might be found in or around an American household. They perform some simple solubility and reactivity tests and compare results with their classmates by use of a flip chart on which the results are summarized. Their purpose the first week is to identify one or two classmates who share the same sample. The second week, authentic samples are provided, and the teams identify their common unknown by comparison of its properties with the knowns. We encourage final comparison to be on a quantitative basis. 2. In “Properties of Antifreeze-Water Mixtures”, each student is assigned a weight percent and prepares a mixture of ethylene glycol and water of that composition. He or she then measures its initial boiling point, density, and viscosity (falling ball method). The class data are entered into spreadsheets and printouts of all class data are provided before the students leave. The second week, they are given an unknown mixture and determine its composition by whatever measurements they choose to use, in comparison with the aggregated class data. Despite large scatter in the class data, 80% of the students identify the unknown composition to within 5%. 3. In the three-week group of exercises dealing with aspirin, students synthesize a sample of aspirin the first week by a standard method. During the next two weeks, they analyze their product and commercial samples by two different methods, which allows comparison of convenience and reliability of the two methods as well as comparison of the samples themselves. Similarly, two complementary methods are used in determining calcium in antacids later on. 4. In “Identification of Plastics”, plastic packaging materials, identified initially by their recycling codes, are characterized according to density, solubility, and responses to heating. The behavioral profiles are then used to identify unknown plastic samples. 5. Similarly, in “Textiles and Dyeing”, samples of six common fibers, both natural and human-made, are subjected to a battery of tests involving elemental composition, chemical behavior, solubility in organic solvents, and response to dyeing. Identification of unknowns is then possible by comparison with the knowns. Student success in identifying both the plastics and the fibers is increased by willingness to do side-by-side comparison of knowns and unknowns and by careful observation of responses. Accuracy of identification in each case is 80–90%. Student Evaluations Student response to the new laboratory program has generally been positive. On a scale of 4.0 (very favorable) to 0.0 (very unfavorable), responses are favorable to working in groups of two or three (3.30) and to bringing in samples (3.05). They were nearly neutral (2.24) to working with pooled section data, as in the antifreeze exercise. The exercises found most interesting by students were synthesis of polymers (3.08), paper chromatography of food dyes (3.04), textiles and dyeing (2.96), and determination of zinc on galvanized nails (2.95).
1024
Week
1 2
Lab Activities
Source
First Semester Check-in. Discussion of course requirements, — goals, and methods. Introduction to laboratory measurements Locally prepared Household “Chemicals”
3 4 5 6 7 8 9
Identification of household “chemicals”: experiment with unknowns; form teams Household “chemicals” continued. Identify unknowns and verify. Graded exercise Analysis of hydrogen peroxide by titration Bring your own peroxide Analysis of household bleach by titration. Graded exercise Properties of antifreeze-water mixtures Antifreeze-water mixtures continued. Graded exercise Determination of zinc on galvanized nails. Bring your own galvanized nails
Extended and adapted from 4 Extended and adapted from 4 (5 ) (6 ) Adapted and extended from 7 Adapted and extended from 7 (8 )
Food and Drink 10 11
12 13
Food dyes: spectroscopy and Beer’s law. Identification of food dyes: paper chromatography. Bring your own food colors or colored foods. Graded exercise Acid content of fruit juices and soft drinks. Bring your own beverages Strength of vinegar by acid-base titration Graded exercise
(9 ) (10 )
(11 ) (12 )
Second Semester Pills 2 3,4 4,3 5
6
7
8 9
Synthesis of aspirin Aspirin purity by pH titration Bring your own aspirin pills Colorimetric determination of aspirin Bring your own aspirin pills Determination of molar mass and pKa of unknown acid by pH titration. Graded exercise Colorimetric determination of iron in multivitamins. Bring your own vitamins. Fe unknown. Graded exercise Determination of calcium in antacids and diverse natural materials. Bring antacids, shells, or other calcium source Complexometric titration of calcium Determination of vitamin C in food products Bring your own beverages or vitamin C. Vitamin C unknown. Graded exercise
(13 ) Locally developed Adapted from 14 Adapted from 15
(16 )
Locally developed Adapted from 17 Adapted from 18
Plastics and Fibers 10 11 12 13
Identification of plastics Bring your own plastic samples Synthesis of polymeric materials Bring your own white glue Textiles and dyeing. Graded exercise Kinetics of bleaching
Journal of Chemical Education • Vol. 73 No. 11 November 1996
Adapted from 19 Adapted from 20 Adapted from 21 Adapted from 22
In the Classroom
Found least interesting were the unknown acid (2.08), determination of aspirin purity by colorimetry (2.13) and pH titration (2.28), and vinegar titration (2.42). These less popular exercises tended to be graded exercises and exercises requiring more extensive calculations. Student assessments of educational quality closely tracked their assessments of how interesting they found the exercises. Overall, student course evaluations, as conducted by anonymous university questionnaires, improved by 0.5 to 0.7 units (on a 7-unit scale) in the category “I would strongly recommend this [course] to a friend,” and by 0.4 to 0.6 units in the category, “I have learned more…than from other…courses…of similar size and level.” Further Development We have begun to introduce FTIR methods into the laboratory program. These will be used initially to assist in identification of household “chemicals” and the unknown acid, and to investigate internal combustion engine exhaust gasses. They will be applied to qualitative analysis of aspirin, vitamin C samples, and plastic samples. We hope to introduce an open-ended exercise on comparison of synthetic and “organic” vitamin C using student-initiated means, including infrared analysis and acid–base and redox titrations. Acknowledgments We gratefully acknowledge the participation of our colleague Robert Schneider in the implementation of this
program. Expansion of the program through incorporation of infrared has been made possible by support of the National Science Foundation’s Division of Undergraduate Education through grant DUE-9552250, which we also acknowledge with gratitude. Literature Cited 1. An analogous focus in an analytical chemistry laboratory has been described: Sherren, A. T. J. Chem. Educ. 1991, 68, 598–599. 2. Neidig, H. A., Ed. Modular Laboratory Program in Chemistry; Chemical Education Resources, Inc., P. O. Box 357, Palmyra, PA 17078. 3. Kandel, M. J. Chem. Educ. 1989, 66, 322–323; 1988, 65, 782–783. 4. Solomon, S.; Fulep-Poszmik, A.; Lee, A. J. Chem. Educ. 1991, 68, 328–329. 5. Deckey, G. MLPC Module ANAL-335; see ref 2. 6. Wolthuis, E. MLPC Module ANAL-416; see ref 2. 7. Flowers, P. A. J. Chem. Educ. 1990, 67, 1068–1069. 8. Burgstahler, A. W. J. Chem. Educ. 1992, 69, 575–576. 9. Gillette, M. L.; Neidig, H. A. MLPC Module ANAL-361; see ref 2. 10. Markow, P. G. MLPC Module ANAL-372; see ref 2. 11. Fuchsman, W. H.; Garg, S. J. Chem. Educ. 1990, 67, 67–69. 12. Neidig, H. A.; Spencer, J. N. MLPC Module ANAL-395; see ref 2. 13. Glogovsky, R. L. MLPC Module SYNT-439; see ref 2. 14. Street, K. W. J. Chem. Educ. 1988, 65, 914–915. 15. Forland, K. S.; Hauge-Nilsen, G. S. J. Chem. Educ. 1991, 68, 674–675; Griswold, J. R.; Rauner, R. A. J. Chem. Educ. 1990, 67, 516–517. 16. Atkins, R. C. J. Chem. Educ. 1975, 52, 550. 17. McCormick, P. G. J. Chem. Educ. 1973, 50, 136–137. 18. Bailey, D. N. J. Chem. Educ. 1974, 51, 488–489. 19. Bowen, H. J. M. J. Chem. Educ. 1990, 67, 75–77; Cloutier, H.; Prud’homme, R. E. J. Chem. Educ. 1985, 62, 815–819. 20. Sherman, M. C. Polymers in Chemistry: Experiments and Demonstrations; Workshop presented at 12th Biennial Conference on Chemical Education, University of California–Davis, 2–6 Aug. 1992; Casassa, E. Z.; Sarquis, A. M.; Van Dyke, C. H. J. Chem. Educ. 1986, 63, 57–60; Chasteen, T.; Richardson, B. Experience the Extraordinary Chemistry of Ordinary Things; Wiley: New York, 1992; pp 229–244. 21. Flachskam, R. L., Jr.; Flachskam, N. W. J. Chem. Educ. 1991, 68, 1044–1045; Allan, J. J. Chem. Educ. 1990, 67, 256–257; Fieser, L. F.; Williamson, K. L. Organic Experiments, 4th ed.; Heath: Lexington, MA, 1979; pp 333–344. 22. Corsaro, G. J. Chem. Educ. 1964, 41, 48–50.
Vol. 73 No. 11 November 1996 • Journal of Chemical Education
1025
