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Chapter 6
Incorporating Experimental Design into a Stand-Alone Undergraduate Physical Chemistry Laboratory Course Molly B. Wilker* Department of Chemistry, Luther College, 700 College Drive, Decorah, Iowa 52101, United States *E-mail:
[email protected]
Implementing research projects into undergraduate laboratory courses can provide high-impact learning experiences for students by creating a space for developing skills such as asking researchable questions, designing experiments and communicating results, all of which are highly desirable for future employers. However, carrying out research projects in a laboratory course without a companion lecture component can present challenges. This chapter outlines a laboratory instruction model for integrating research experiences into a semester-long physical chemistry laboratory course in which students are first guided through traditional lab protocols to become familiarized with measuring and modeling chemical kinetics for a variety of systems. The protocols provide students with examples for experimental questions, which students use to identify the design choices within each procedure. As the semester progresses, the students are asked to make an increasing number of experimental decisions, which culminates with the design and implementation of an independent project.
Introduction The importance of laboratory work in an undergraduate chemistry curriculum is widely accepted as essential for training chemists (1, 2). A broad range of approaches to upper-level, undergraduate laboratory instruction exist including © 2018 American Chemical Society Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
expository, inquiry, discovery, problem-based, and authentic research activities (3). Each approach has its strengths and weaknesses in terms of targeted student outcomes. Recent studies have shown that engaging in inquiry and research project laboratory work has a high-impact on learning for undergraduate students in chemistry (4–13). However, replacing traditional expository laboratory experiments with inquiry investigations and research projects can present many challenges including increased time investment, logistics, and uncertainty (13, 14). A particular challenge in the physical chemistry laboratory is that students need to first learn the mathematical models and practice the data analysis necessary to design and undertake a novel physical chemistry research project (15, 16). This chapter presents an alternative laboratory model that provides instructional scaffolding to help students develop the skills necessary to propose a research question, develop a project proposal, and carry out a short-term research project. Traditional, expository laboratory instruction consists of well-tested experiments meant to introduce or reinforce important topics (3). During these traditional laboratories students gain confidence in their laboratory technique, use of instrumentation and data analysis displayed by their ability to accurately repeat findings and answer prewritten questions about their outcomes. A benefit of these traditional laboratories is that the expected results create a controlled learning environment and ease student assessment. With these traditional methods, the typical undergraduate student is focused on collecting the required data, but demonstrates little ownership of the work and a lack of interest in deeper understanding. Integration of inquiry-based instruction and in-class research experiences into the laboratory setting benefits the students by encouraging them to look beyond the repetition of a result to chemical logic and problem solving skills (4–11). While these engaging types of laboratory instruction are broadly varied, in each case students are expected to play a larger role in developing how to approach a problem. By reframing the student experience to consider that scientific research deals with the unknown, students create their own understanding of a system. These more authentic science experiences create a space for developing skills such as asking researchable questions, designing experiments and communicating results, all of which are highly desirable by future employers. Therefore it has been accepted that this model of laboratory instruction is preferred over the expository model. Although the paradigm for chemical laboratory instruction is making a shift away from the traditional expository instruction style, the transition to a laboratory instruction with the unknowns of inquiry or authentic research can present a challenge for both students and instructors (14). While the students taking physical chemistry laboratory courses are almost always juniors or seniors and have the maturity to undertake increasingly independent work, they may not be prepared to jump directly into an authentic research experience even with instructor support. In recent years, many chemistry departments have separated the advanced undergraduate laboratory courses, including physical chemistry, from the lecture courses. This leads to a wide variety of preparation upon enrolling in the laboratory course. Without prior understanding of the physical 84 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
chemistry concepts, students are not able to create effective research plans when presented with a research question to pursue. Furthermore, in many cases, the students’ laboratory experiences from the first two years in a chemistry program function to reinforce important theories and laboratory techniques, but often, time is not dedicated to teaching the ability to ask scientific questions and pay attention to the details necessary for designing an experiment to further understand a chemical system. Although implementing research experiences into lab courses is desirable, effective transitioning from traditional instruction to independent projects is crucial. The laboratory instruction approach presented here provides a design for transitioning students from traditional expository laboratory instruction to independent research projects in the context of an upper-level undergraduate physical chemistry course with a focus on chemical kinetics. During the first half of the semester, students are introduced to relevant techniques for data collection, kinetic theories, and methods for fitting data to kinetic models through a combination of instructional events and inquiry-based laboratory work. During this first phase, the students are given instruction for data collection, but are prompted with specific experimental design questions and use primary literature to resolve the missing steps of each procedure. During the second half of the semester, students write a research project proposal to expand their understanding of one of the chemical systems that they began investigating during the first half of the semester. Unlike many other in-class research project instruction models, the students are not provided with a research question, but instead are given the responsibility of identifying an interesting scientific question based on their preliminary studies from the first half of the semester. From the initial proposal to the final presentation of their work, students demonstrated increased ownership of their research projects. This chapter includes details of the course’s design and presents instructor observations and student feedback, all of which support the effectiveness of this laboratory instruction model for improving student learning and the practice of important, transferrable skills.
Course Organization Luther College is a primarily undergraduate institution located in rural Iowa. The Department of Chemistry at Luther College graduates between 10−20 chemistry majors each year with >90% of the majors graduating with our liberal arts chemistry major (minimal requirements) and only a few students each year receiving an American Chemical Society-accredited degree. With a fluctuating number of majors each year, we offer our upper-level (junior and senior level) laboratory courses separated from lecture courses. This increases the flexibility of scheduling for both our students and the chemistry faculty. The separated lecture and laboratory courses in each chemistry sub-discipline are not only offered for separate enrollment, but also do not have prerequisite requirements beyond sophomore-level coursework. While this model allows for flexibility in scheduling (something we value to allow our students to pursue many aspects of 85 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
their liberal arts education including studying abroad), it increases the diversity in preparedness of the students for the course. When students enroll in the Physical Chemistry Laboratory, the assumed knowledge of chemical kinetics is from General Chemistry and Organic Chemistry coursework. The laboratory is held for two, three-hour sessions each week. Meeting six hours each week allows time for pre-lab lectures to teach new kinetic models including complex reaction mechanisms. Lab groups rotate through laboratory protocols because of instrumentation limitations, which encourages each group to rely on their own skills and allows for individual group meetings with the instructor. By setting aside time during formal laboratory time for data analysis, the instructor can work directly with small groups of students on fitting data to kinetic models. The primary objectives of this course are to:
• • •
Explore how chemical changes are observed and what factors influence reaction rates Learn the mathematical framework used to describe the timescales of chemical reactions Gain firsthand experience with the aspects of designing and carrying out a new laboratory experiment
To achieve these course goals throughout the semester, a series of activities, outlined as a timeline in Table 1, were created. During the first half of the semester the students worked in small groups (2-3 students per group) and were directed through a series of experiments designed to teach laboratory techniques, instrumentation, and data analyses. These experiments are outlined in Table 2 with specified kinetic models that are introduced with each protocol. Pre-lab lectures and the procedures themselves were used to introduce the students to each new concept. Throughout the course, students primarily used the software designated for each instrument as well as spreadsheet programs to manipulate, plot, and fit data to simple regression models. In the experiment, Oxidation of Glutathione by Cr(VI), students were introduced to modeling using numerical methods using Berkeley Madonna, a differential equation solving program. The first experiment, Reduction of Methylene Blue by Ascorbic Acid, was presented to the students as a traditional lab. During this first expository-style lab, students were prompted to identify specific design elements and to reflect upon why those choices were used. As the semester progressed, students were responsible for making an increasing number of protocol choices. During this initial phase, students were provided with a chemical system and were prompted with an experimental question, but they were responsible for deciding what data to collect (i.e. number of data points needed, spacing of data points, range of variable tested). The use of primary literature was encouraged to guide the decision-making process. Due to these experimental choices, the outcomes varied for each lab group and this encouraged collegial conversation between groups. Prior to each laboratory period, students were required to create a complete, experimental plan. This plan involved making the prompted experimental decisions, which required 86 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
an understanding of the premise of the lab protocol and demonstrated the value of reading literature. Students maintained individual electronic lab notebooks during the initial phase of experiments. Awareness that not only their results, but also procedural notes would be needed in the latter half of the semester provided motivation for detailed note keeping. Notably, students were required to include ideas for further testing of each chemical system in their notebooks. To facilitate a transition into the project phase of the semester, the students were asked to formally reflect upon the content and lab skills they learned during the first part of the semester. During this reflection, students identified themes within the experimental goals and correlated the choice of kinetic models with the independent variable tested. Group conversation around these reflective questions was then transitioned directly into the design of group research projects. The instruction given for this project was to further investigate one of the chemical systems from the lab protocols completed in the first part of the semester. The student projects were evaluated upon their ability to demonstrate the following:
• • • •
Understand and explain the rationale of a chemical kinetics or thermodynamics question and experiment Design experiments to test hypotheses Accurately analyze and interpret data Communicate results, revise hypotheses and propose experiments for further testing
Table 1. Schedule of activities throughout the semester
a
Timeline
Durationa
Description
Week 1
3 hours
Lab overview and kinetics introduction
Weeks 2-8
45 hours
Established lab protocols: learning experimental techniques and analyses
Week 9
6 hours
Reflections, project design discussion, and proposal writing
Week 10
3 hours
Project proposal meetings and revisions
Weeks 11-13
18 hours
Project experiments
Week 14
6 hours
Poster peer review, presentations & project reflections
Scheduled in-class time
87 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
Table 2. Laboratory procedures matched with the kinetic model(s) and analytical technique(s) being presented in each protocol Procedure Title
Kinetic Model
Analytical Techniques
Reduction of Methylene Blue by Ascorbic Acid (17)
Determination of reaction orders and rate constants
UV-vis spectroscopy
Fast Reaction: Crystal Violet with Hypochlorite (18)
Integrated rate law expressions
UV-vis spectroscopy with stopped-flow apparatus
Investigating the Mechanism of Heteroaromatic Decarboxylation (19)
Solvent kinetic isotope effect and Eyring transition-state theory
UV-vis spectroscopy with temperature control
Dimerization Equilibrium of a Cyanic Dye (20)
Equilibrium and van’t Hoff equation
UV-vis spectroscopy with temperature control
Oxidation of Glutathione by Cr(VI) (21)
Sequential reaction mechanisms and preequilibrium approximation
UV-vis spectroscopy monitoring multiple wavelengths
Enzyme Kinetics of Lactase (22)
Michaelis−Menten enzyme kinetics
UV-vis spectroscopy
Isomerization of Congo Red (23)
Photochemistry and acid-base catalyzed reactions
Flash photolysis
Photophysical Properties of 2-Naphthol (24)
Photochemistry and diffusion-controlled reactions
Fluorescence spectroscopy
Quenching of [Ru(bpy)3]2+ emission with transition metal cations (25)
Fluorescence quenching, Stern-Volmer relations, and electron transfer
Fluorescence spectroscopy and time-correlated single photon counting
Students were arranged into new lab groups comprised of students from a mix of the initial lab groups. This arrangement provided each new group with multiple data sets from the previous experiments to inform the project proposal. The students were encouraged to share and compare data to simulate a collaborative research group. Each lab group created a project proposal that included experimental protocols, a list of requested chemicals and supplies, and a timeline for project work. The proposal guidelines also required a description of hazards and steps to minimize risks in the lab. During this process, the instructor acted as a mentor to guide the decision-making process. The proposals went through a series of revisions until the faculty facilitator approved the plans. During the project work, each group collaborated on a shared electronic lab notebook. The use of an electronic lab notebook platform allowed for notebook 88 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
sharing and facilitated collaboration on the project. During the final week of the semester, each group was responsible for creating a poster for the collegewide poster session. Prior to printing, the posters went through a round of peer reviewing and revisions. A rubric has been developed to assist in the grading of the research projects (Table 3), which were worth 30% of the overall course grade. The students were aware of this rubric. Each group’s project work was graded according to the rubric, but each individual submitted an evaluation of their group members’ participation in the project work, which was taken into account during assessment. Notably, while the students were directly graded on their technical proficiency and correct data analysis during the first phase of the semester, during the project phase, the success of the project was evaluated upon problem solving, interpretation of results and scientific communication.
Implementation Observations Evaluation of the effectiveness of the course model was done through direct observation of student progress. The students’ progress toward experimental proficiency and confidence in the approach to a new research question was observable by the instructor throughout the course. Lab notebooks and final presentations show the extent to which the students understand the significance of their results and are able to effectively communicate those results. In each of these aspects, the course was successful. As we expected, the students devoted time to decision-making, finding relevant information, and re-evaluating errors. Because they were predicting spectral trends prior to beginning experiments, they recognized when data did not look as expected in real time. Initially, the students were uncomfortable with “messy” data and believed that they must be doing something incorrectly, but over the course of the semester, they gained confidence in their abilities and were able to accept and evaluate the real data. Some of the best learning moments during the course were the result of a group of students troubleshooting an experiment. When students were brainstorming ideas for their project proposals, they were able to identify variable experimental parameters for the basis of their research questions such a system’s as temperature, pH, solvent, concentration, or the identity of a reactant. Example research questions from student projects include, “What solvent viscosity is necessary for the rate of deprotonation of 2-naphthol to become diffusion controlled?” and “What is the role of temperature on the inhibition of lactase activity?” The fluorescence quenching of [Ru(bpy)3]2+ was a popular system for projects with students asking questions such as, “What effect does changing the reduction potential of the metal ion have on the fluorescence quenching of [Ru(bpy)3]2+?” and “Can the thermodynamic properties of [Ru(bpy)3]2+ fluorescence quenching be calculated using temperature-controlled experiments?” 89 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
Table 3. Grading rubric for research projects Points/100
Task
Notes for evaluation
Project design proposal: Was the project well thought out and articulated? Should include a clear purpose, hypothesis, and experimental plan.
15
Written project proposal
5
Project timeline and supply & chemical list
5
Project proposal revisions
Expected to be prepared to discuss the details of the proposal with instructor during review. Proposal revisions must be approved before lab work may begin.
5
References
Must include at least 2 primary literature sources.
Experiment execution:
15
Lab work and notebook
Expected to work diligently and abide to lab safety rules. Carefully record all experimental details and results in notebook.
10
Analysis of results
Were results comparable to what was expected in proposal and/or literature?
10
Conclusions
Address conflicting or missing data. Revise hypothesis and include ideas for further testing.
Project presentation & poster: 10
Peer review
Provide constructive feedback to peers on poster drafts and practice presentations.
10
Final Poster
Poster should summarize your work concisely and attractively, to help publicize it, and to generate discussion.
15
Summary and Presentation
Prepare a 2-sentence summary of your project and 2 minute explanation of your work.
The students took ownership of their projects as indicated by their disappointment when an experiment did not work out as planned and their excitement over a good result. Not only did the students take pride in their own projects, but because each group had a hand in creating the preliminary data for each other’s projects, each student was invested in the success of the other groups’ projects as well. The entire class was interested in learning about the variety of project ideas and the progress of the other groups. Frequently, the students would gather in the lab early to chat about their respective projects, 90 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
which motivated each group to engage in interesting research questions and to do high-quality lab work. This supportive sense of community within the group of lab students was invaluable when it came time to peer-review posters and presentations. Each student had a firm understanding of the other projects and was able to contribute valuable feedback. The students were proud to share their findings at the college-wide poster session. One of the limitations of this approach is that the research projects in this course are limited to a short period of time, unlike many other in-class research experiences that continue the same project over multiple semesters or years. This stifles the ability to sustain a project long-term and continue to build a body of work for publication. At the end of the semester, students were encouraged to enhance their learning process by providing reflections on their experiences. The student comments about the course have been unanimously positive. Selected student quotes are included below: • • • •
•
•
•
Student A: “I learned a lot about/got a lot better at trouble-shooting experiments when things aren’t going exactly to plan.” Student B: “Doing the project forced me to think much more deeply about the theory behind the reactions that we were studying.” Student C: “This project emphasizes planning and the need to have a feasible hypothesis for testing.” Student D: “I learned how much time and thought actually goes into planning. … Looking at the schedule, it seemed like we would have so much time but that wasn’t the case.” Student E: “I liked how this course was split into two parts, planned labs and projects. I think that this was really helpful for me in learning about project planning and executing.” Student F: “I found pretty much all of the labs to be useful and I appreciated that each lab dealt with some new topic or procedure so there wasn’t too much overlap between the labs. I especially found the research project to be a huge strength of the course. The research project was such a valuable part of the course because it helped to push students and also helped to teach a lot of important skills that are often overlooked in lab classes (such as project design, literature research, problem solving, and presentation skills).” Student G: “I think that she (the instructor) also created a very safe environment where students felt comfortable sharing their work. The most prominent example of this was during the practice poster presentation, when each group presented their posters and received valuable feedback from both Professor Wilker and their peers.”
Observations from the student responses include themes of surprise and resilience. Anecdotally, students commented on “feeling like a real scientist” with genuine appreciation for the opportunity and remarked that the breadth of experiences gained in this laboratory course (i.e. oral communication skills, teamwork, critical thinking, problem solving, and resilience) had helped them 91 Teague and Gardner; Engaging Students in Physical Chemistry ACS Symposium Series; American Chemical Society: Washington, DC, 2018.
prepare for future work. From both the student and instructor perspectives, the redesigned course was a valuable learning experience.
Conclusions A new approach to the undergraduate physical chemistry laboratory curriculum was created with a scaffolded approach to transitioning from an expository-style laboratory instruction method, which is necessary for teaching new concepts in a course without a lecture component, to student-driven research projects. The laboratory design was based on the content of chemical kinetics but framed around the theme of project design. Numerous activities have been developed to support student mastery in data collection for a chemical reaction and applying a kinetic model to analyze that data. Though it was crucial to include a component in this course dedicated to learning and practicing kinetic modeling when students were not required to take a physical chemistry lecture that coincided with the laboratory, this model is also applicable for programs in which the kinetics of complex reaction mechanisms is not covered in detail during lecture (26). Throughout the semester, the students were engaged in creating their own scientific questions around the chemical systems they were studying. Another important outcome of this approach was the development of a sense of community. This collaborative learning environment helped students engage in conversations that deepened their understanding of chemical phenomena and fostered problem-solving skills. The majority of students indicated positive response to the lab and found value in the approach. This instructional method provides a solid foundation for students’ preparation for their careers as professional scientists. The redesigned course presented here was successful as a case study with a small number of students, and as the course model is implemented in the future, its effectiveness will continue to be evaluated though assessment of student learning and with surveys of student perceptions.
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