edited by SUSAN H. HIXSON National Science Foundation Washington, DC 20550
Highlights
CURTIS T. SEARS, JR. Georgia State University Atlanta, GA 30303
Projects supported by the NSF Division of Undergraduate Education Curriculum Using the Unique Capabilities of Lasers Gerald R. Van Hecke and Kerry K. Karukstis Harvey Mudd College Claremont, CA 91711
Numerous recent workshops and symposia have addressed the status of the nation's undergraduate educational programs in the sciences. In a report from the National Science Board's Task Committee on Undergraduate Science and Engineering Education (Neal Report) (11,two key concerns relevant to introductory chemistry programs are articulated: the lack of motivation for students to pursue careers in chemistry; and, the existence of deficient laboratories with inadequate and obsolete equipment. The workshon on Undergraduate Education in Chemistry (2) report states that "students o h n perceive chemistry as an unchanging scientific discipline in which all of'the important discov&ies have already been made." Recommendations to enhance the undergraduate chemistry experience include a call for a more exciting and intellectually challenging curriculum that presents chemistry as a modem experimental science and the need for incorporating new technology of low cost into the design of laboratory experiments. Lasers are well-established research tools frequently used to detail reaction pathways, elucidate molecular structure, and initiate chemical reactions. Now is a n opportune t&e to use these tools in the classroom to enhance and enrich student understanding of chemistry course materials and stimulate interest in the subject. Moreover, now is a critical time to provide the student more accurate pictures of the dynamic nature of chemistry with its responsiveness to technological advances. Our project addresses these issues with a fresh approach designed to illustrate fundamental concepts of chemistry with cuttingedge technology. Our goal is to design a fresh approach to the General Chemistry curriculum a t Harvey Mudd College through the development of lecture demonstrations and experiments that involve the unique capabilities of laser light sources. The use of readily accessible lasers will enable our undergraduates to experience the application of modern tools to classical questions in chemistry. These laser-based activities will augment our presentation of fundamental chemical concepts in order to enrich the students' understanding of the course material and stimulate their interest in chemistry. Our demonstrations advance the teaching of thermodhamics, kinetics, acid-base eqmhbria, chemical bonding, and atomic spcctroscopy. Typical Demonstrations under Development As examples of demonstrations under development, consider the two simple cases below. The kinetics of the classic acid hydrolysis reaction of sucrose to produce glucose and fructose is well-suited for demonstration by measuring the amount of rotation of the plane of polarized light. Dextrorotatory sucrose is con-
verted a t a reasonable rate to an equimolar and levorotatory mixture of glucose and fructose a t mom temperature (3).The extent of rotation of the plane of polarization of the laser beam may be followed with a polarized sheet at the exit of a suitable reaction tube. Polarizability is oRen use to explain aspects of chemical bonding and yet it is generally a difficult concept for students to grasp. Light scattering is highly sensitive to the polarizability of a given substance. Measuring the simple laser light scatter of CC4 versus CL demonstrates the difference in the polarizability of large, electron-rich compounds without dipoles compared to smaller, less eledronrich, dipole-freemolecules. Cases of very low polarizability even with strong dipoles can also be demonstrated, with water being an outstanding example. Acknowledgement This work has been partially supported under the National Science Foundation award DUE 9155909. Literature Cited 1. ~ ~ t i ~Science n a l Board TsskCommittee inundergraduate %en= andEngneering Education, Undergmduote Sciences, Mofhemolies, and Engi-rLng Edueotion, National Science Board, Waehington, D.C., 1986. 2. The Workshop on Undergraduate Education in Chemhtry, Report on the Nofianol Science Founda"on Diaciplinaly WorkPhops an Undergrsduate Education, National Science Foundation, Washinpton. D.C., 1989. 3. Weir, J.J. J. Cham Educ 1989,66,1035-1036.
Transformation of Chemistry Experiments into Real World Contexts Richard Bayer, Bud Hudson, and Jane Schneider Carroll College and BrookfieldAcademy
One of the most pressing challenges for science educators in chemistry is to provide creative ideas to the pmblems associated with the introductory chemistry course, especially the laboratory component. In the absence of such creativity, students are often uninspired and discouraged from pursuing the discipline as a major. One of the main reasons for this discouragement is that the courses offered present a series of fundamental topics and associated experiments that have no apparent unifying theme and do not relate to real-world experiences. Thus, strong arguments for modifying laboratory programs have been made. For example, some educators have adopted discoverybased formats, others research-based formats. However, many educators are very committed to their personal repertoire of experiments. These experiments have often been developed over many years, relate well to lecture topics and are well understood in terms of experimental details and student rcsults. Thus, many faculty members are not enthus~astlcabout maklng significant changes Hence, a stalemate. On the one hand, sound experiments that are effective and efficient and that incorporate essential techniques for introductory chemistry students. On the other hand, experiments that are unexciting and often not motivating to further study Volume 70 Number 4 April 1993
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One resolution of this dilemma, which has produced exciting results for us, involves setting the existing experiments within local real-world contexts. That is, to have our students identify with local laboratory personnel working on realistic problems which are addressed by the specific exoeriments to be done. In our situation. our students as&me they are laboratory technicians in a consulting laboratory. This facilitates encountering a wide range of chemistry-related problems. Alternative contexts, depending on local situations, might be industrial, municipal, or governmental laboratories. Each experiment, therefore, is set within this context and the introduction, goals and obiectives rewritten (incorporated in a scenario) to just& its performance. This process is called "transformation" of the experiment. The results yield experimental titles such as the following (original titles in parentheses): "Chemical Reactions in a Landfill Site" (The Atomic Weight of Cu); and "Reduction of Gear Size" (Acid-Base Reactions). Let's explore the "transformation" of the latter experiment as an example. The chemistry instructor selects a typical acid-base experiment at the college or high school level. Careful characterization of the experiment lists the chemicals used and the operations involved, for example, preparation of a standard acid such as potassium acid phthalate, preparation of a base such as sodium hydroxide, titrations to standardize the base, use of indicators or pH meter, and determination of the concentration of an unknown acid. The overall goal usually involves the unknown acid concentra*inn
Suppose a local machine shop making gears has periodic problems with the gears beinn oversized after hear treatment, and it is necessary to remove small amounts of surface metal using an acid solution. The concentration of this acid solution must be monitored in order to estimate the number of gears that can be serviced with a given quantity
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of acid. Thus, a local setting and a real problem. In our case. the machine shop is a real operation located two mile; from the college. he story invhves real people with real personalities who are involved in the local community. If thk introductory chemistry laboratory sections are organized as a consultant laboratory, the research director (chemistry instructor) could receive a phone call from the machine shop owner asking for help in solving the acid bath problem. The students, as employees, are asked to help solve the described problem and provide answers by the next week. It is still necessary to do all the steps of the original experiment (preparation of standard acid, titrations, etc.). However, the overall goal is more "relevant," and the "scenario" allows a better description-and thus understanding-of the complex dynamics of real-world problem solving. - Many questick may be raised about this transformation orocess. How does the instructor find out about useful stories that are going on in the local community? How does one fit a scenario to the exact needs of the existing experiment? How are the personalities ofthe people involved, the urgency of the results, and the aspect of unknowns woven into the scenario? We have developed a "transformation process" that allows chemistrv instructors at both colleee and hieh school levels to add real world scenarios to existing experiments. The process describes how to look for people who have stories,how to ask specific questions of (he experiments, and how to listen to responses durinz intenriews to pick out scenario gems. n u s , w t h a mod& amount of effort, an instructor's laboratory sequence can be "transformed."
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Acknowledgement This work has been partilly supported under the National Science Foundation Grant No. DUE 9150795.
