Customized Laboratory Experience in Physical Chemistry - Journal of

In the Laboratory

Customized Laboratory Experience in Physical Chemistry Karen J. Castle* and Stephanie M. Rink Department of Chemistry, Bucknell University, Lewisburg, Pennsylvania 17837, United States *[email protected]

Much work has been done over the years to improve the quality of the laboratory experience in undergraduate coursework. Many successful models have been developed around the themes of integrated laboratory (1-7), guided inquiry and inquiry-based laboratory (8-12), research-based laboratory (13-16), and independent student projects (17-19). Although there have been some successful initiatives in the physical chemistry laboratory (3, 9), physical chemistry instructors may be the least likely to adopt nontraditional laboratory approaches. There are certainly challenges associated with the implementation of nontraditional laboratory designs, including that they often require more time than traditional approaches. Physical chemistry is considered by many students to be the most difficult undergraduate course in the chemistry major, and often concepts are only truly understood when they are seen in the laboratory. Many instructors worry about having to sacrifice content in order to implement a more creative laboratory experience. The model outlined in this article is an attempt at a compromise between the traditional physical chemistry laboratory structure and a completely open-ended approach. This model puts more control into the hands of the students without sacrificing the rigor or thoroughness of a content-driven laboratory. Students At this university, the second-semester physical chemistry course is populated primarily by third-year students pursuing a bachelor of science degree in chemistry. Occasionally, students pursuing a bachelor of arts degree in chemistry or a bachelor of science degree in biochemistry, cell biology, or physics will take the course as a chemistry elective. Prerequisites for the course include two semesters of organic chemistry, one semester of inorganic, one semester of analytical chemistry, and two semesters of physics. The typical enrollment is 8-14 students who are divided into two laboratory sections. The subject matter of the course focuses on atomic and molecular structure, quantum mechanics, symmetry, spectroscopy, and statistical thermodynamics. However, this laboratory design could easily be translated into other small, upper-division courses with a significant laboratory component. The design is best for small courses with eight or fewer students per laboratory section, and it would be difficult to implement in larger courses. If instrumentation to be used by the students is located in different rooms, reliable teaching assistants are indispensible. It should also be noted that the implementation of this laboratory design is very instructor-intensive in the first year and easier in subsequent years. Goals In the customized laboratory experience in physical chemistry, students use laboratory work to explore and solidify their 1360

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understanding of the major concepts presented in the accompanying lecture. At the same time, students should feel more in control of their own education because of the added flexibility and responsibility that they are given in the laboratory. If the laboratory experience is more interesting to each student, he or she is likely to better retain the material. In addition, the special project component gives chemistry majors invaluable firsthand experience with all aspects of designing and carrying out a new laboratory experiment. Laboratory Design In the first week of laboratory, students are introduced to the flexible laboratory design. They complete an introductory exercise where they read through the laboratory manual and come up with an initial outline of their laboratory schedule. (They are later allowed to change as many times as they wish.) In the subsequent nine weeks of laboratory, the students are asked to complete seven experiments including at least one experiment from each of five categories. The remaining two experiments can be chosen from any of the regular categories or from the miscellaneous category. The categories and experimental choices currently available are shown in Table 1, although these experiments are constantly being updated and new ones are being added. By forcing students to complete at least one experiment from each category, they will necessarily be exposed to each of the major themes for the semester. The experiments are all designed to be the first introduction of new concepts from the course; thus, they may be completed in any order. The two extra weeks of time may be used as bye weeks whenever the students have particularly busy schedules. Students may work individually or in pairs; many choose to work with a partner sometimes and individually sometimes depending on which experiments they wish to complete. They are allowed to change their minds and select different experiments as the term progresses and they are exposed to new topics. As they learn more in the classroom and gain more experience in the laboratory, it is natural that their interests may change. It is not uncommon for a student to choose to perform an experiment because they do not really “get” a topic from class and want to spend more time on it working closely with the instructor. Students must write four formal lab reports and three mini reports on their seven chosen experiments. Full lab reports are written in scientific journal-style, whereas mini reports consist of only the appropriate data and error analysis. Students can choose which experiments to write up as full reports with only two constraints. First, they are required to write up one of their first two experiments as a full laboratory report so that everyone has something to bring to class for a peer review early in the semester.

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Vol. 87 No. 12 December 2010 pubs.acs.org/jchemeduc r 2010 American Chemical Society and Division of Chemical Education, Inc. 10.1021/ed1005097 Published on Web 10/14/2010

In the Laboratory Table 1. List of Experiments for the Physical Chemistry Course Experimentsa

Category Quantum Mechanical Models

Spectrum of a Particle in a Box (20) Spectra of a Particle on a Ring and a Particle on a Sphere (21- 23)

Computational Chemistry

Computing Normal Modes of Vibration and Predicting IR Activity Computing Electronic Transitions in Aromatic Compounds

Emission Techniques

Solvatochromism of a Fluorescent Dye (24) Solid State Lasers and Radiative Properties of a Ruby Crystal (20) Emission and Lifetimes of Fluorescent Minerals Kinetic Behavior of Lightsticks (25, 26)

Spectroscopic Determination of Molecular Parameters

Absorption Spectrum and Dissociation Energy of Iodine or Bromine(20) Infrared Spectra of HCl and DCl (20)

Statistical Thermodynamics

Diode Laser Measurements of a Boltzmann Distribution (27) Determination of Rotameric Stability using Infrared Spectroscopy(28) Enthalpy and Entropy of Sublimation of Iodine (20)

Miscellaneous

Laser Scattering by Sulfur Particles (29) Kinetics of Ferrioxalate Photochemistry Spectrophotometric Determination of Iron Content in Food (30) Solid State FTIR of Caffeine or Pain Relievers Spectrophotometric Analysis and Modeling of Sunscreens (31)

a

Experiments are updated each year and new experiments are added periodically as they are developed.

The second constraint is that at least half of the full lab reports and at least one mini report must be submitted by the midpoint of the semester. The latter constraint is helpful for students who tend to procrastinate. In the laboratory manual, students are provided with a grading rubric for each experiment. All mini reports are graded on a 20 point scale, whereas full reports are graded on a 35 point scale. Both types of reports are assessed for scientific content, which may include mathematical calculations, presentation of data in graphs and tables, error analysis, comparison of results with literature values, and answering a series of discussion questions. The extra 15 points allocated to full reports are used to assess the quality of writing, structure of a scientific journal-style paper, proper referencing techniques, and overall effectiveness of the report in conveying the results of the students' work. The laboratory component makes up roughly 30% of the final course grade. The special project component of the course provides students with a unique opportunity to deepen their understanding of a topic that they find particularly interesting. Special projects are chosen by the students working individually. Each student writes a proposal toward the middle of the semester and performs the proposed experiment during the last three weeks of lab. The proposal process includes hazardous materials characterization and development of a plan for waste disposal. A special project culminates in a 15-min oral presentation to the class as well as a formal, journal-style laboratory report. Discussion A flexible lab methodology gives students control of their own learning. Students choose and perform experiments that most interest them from a variety of choices. Students necessarily have to do more of the preparatory work than in a traditional laboratory course, and this personal responsibility seems to promote a higher sense of accountability. This laboratory structure has resulted in students spending more time preparing for

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lab. It appears that they have a better understanding of the material and how the experiments fit in with the course lectures, readings, and assignments. Because the design of this laboratory encourages students to read and understand many experimental options, it also gives them a broader exposure to techniques and applications in the lab. In addition, one 80 min lecture period toward the end of the semester is dedicated to discussing the experiments that were done by the various lab groups: the procedures, the results, and their relationship to the course content. Thus, all of the students have a chance to see the important conclusions from all of the experiments performed that semester, even if they were done by classmates. From the students' perspective, the biggest disadvantage of this laboratory design may be for students who do not have much confidence in the laboratory. Because they are required to do their own preparatory work, they are often anxious about getting started. The experiments usually take longer than they should (and thus, experiments are designed to be a little shorter than the 4-h time blocks that are allocated for the laboratory sections). Another disadvantage is that because not all the students perform the same experiments, there is uneven exposure to topics. This is partially addressed in the lecture devoted to laboratory review, but of course a lecture is not as good at communicating concepts as performing an experiment would be. The advantages of the design to students (the ability to perform more interesting experiments, flexibility in scheduling, better retention of material, etc.) seem to outweigh these disadvantages. Although many chemistry majors choose to take part in undergraduate research, the special project component of this laboratory differs in significant ways from the typical undergraduate research experience. Here the students see their projects through from beginning to end. They come up with their own ideas, do their own literature searches, design their procedures (with guidance from the instructor in the form of individual conferences), write proposals, perform a hazardous waste characterization and think about environmental impacts, carry out

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In the Laboratory Table 2. Examples of Special Projects in the Physical Chemistry Course Special Projects Seashell Pigmentation Analysis Using UV/vis Spectroscopy Laser Induced Fluorescence of Lightstick Dyes (32)

students. Some examples of special projects performed in this course in the last seven years are given in Table 2. Students compiled complete bibliographies in completing their projects and hundreds of references were cited for the experiments listed in Table 2. An abbreviated list is given here where references are only cited for projects that were quite similar to published work.

Phytoremediation and the Uptake of Zinc by Poplar Trees Heavy Metal Contaminants in Cave Water

Assessment

Concentration of CO2 in Soft Drinks: How Soda Goes Flat

Student assessment of the customized laboratory experience has been encouraging so far. All of the respondents in the first two years of implementation either agreed or strongly agreed that the customized laboratory experience was more enjoyable than a traditionally structured laboratory, though this is difficult to interpret because students do not experience a traditionally structured laboratory on the same content. Most of the students, 85%, either strongly agreed or agreed that this laboratory experience helped with their understanding of concepts from the lecture component of the course. Some specific student comments on the customized laboratory experience are listed below.

Constructing a Tabletop Dye Laser Free Ligand to Enzyme Conformation Determination Using NMR Determination of Calcium and Iron in Food by Atomic Absorption (33) Spectroscopic Studies of Doped Sol-Gel Monoliths The Relative Fluorescence Quantum Yield of Highlighter Markers (34) Greenhouse Warming Potentials from the IR Spectra of Atmospheric Gases(35) The Synthesis of Basic Amino Acids in Primitive Earth Conditions Spectroscopic Measurements of the Thickness of Soap Bubbles (36)

• “[The customized laboratory experience] gives us the opportunity to learn about what we are interested in rather than something chosen for us.” • “I was able to spend more time understanding concepts rather than just answering questions for a grade.” • “I liked that everyone could be working independently on separate tasks.” • “The labs are more relaxed and less stressful and allow you to write lab reports when time is available.” • “[The customized laboratory experience] was less predictable than other labs.”

Measurement of Trace Metals in Tobacco and Cigarette Ash by ICP-AES(37) Luminescence Quenching of Ru(bpy)3þ2 Composition and Thickness Determination of a Palladium Nickel Alloy Coating A 4-Step Organic Synthesis and Structure Solving with NMR and IR Constructing a Homebuilt Raman Spectrometer Measuring Breath Alcohol Concentrations with an FTIR Spectrometer(38) Light Emission At Electrodes: Electrochemiluminescence (39) Determination of CO, CO2, NOx, O2, and SO2 in a Coal Plant Air Sample

Conclusion

Chemistry in Photography: Dyeing Black and White Photographs (40)

A new customized laboratory experience has been designed and successfully implemented in the second-semester physical chemistry course. At the beginning of the semester, students choose their own set of experiments from a large array of choices and their own timeline for completion of those experiments. The latter part of the semester is devoted to individual, studentdesigned special laboratory projects. In the customized laboratory experience, more responsibility is placed on the students, thereby encouraging them to take charge of their own learning. At the same time, students are required to complete a vetted experiment on each of the important topics of the accompanying lecture course where they are sure to be exposed to the ideas to which they need to be exposed. Students and instructors alike have responded positively to the design.

Synthesis and Photochemical Characterization of Lanthanide Complexes Fluorescence and the Micellization of Bile Acids 13

C NMR Relaxation Studies of n-Hexanol

Fluorescence and Lifetime Quenching of Iodine Vapor (41) Distortion of Anthracene Spectra Upon Laser Excitation (42) Photoreduction Kinetics of Camphorquinone Infrared Spectroscopy in the Study of Renal Lithiasis IR Vibrational Shifts in Substituted Ketones Experimental Determination of the Spectrochemical Series Fe and Cu Levels in Contaminated Well Water Absorbance and Fluorescence of the Pigments in Olive Oils

Literature Cited

Solid State FTIR of Non-Nutritive Sweeteners

the experiments, redesign them when they do not work as planned, and disseminate their results orally and in writing. It is not common for an undergraduate research assistant to experience all of these things in a research laboratory setting. Originality is not a requirement for special projects. Some students will simply choose an experiment from the literature and modify it to an appropriate scope. The more creative students come up with original ideas. Many of the most successful special projects have been related to specific hobbies of the 1362


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Customized Laboratory Experience in Physical Chemistry - Journal of

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