Article pubs.acs.org/jchemeduc
Using a Thematic Laboratory-Centered Curriculum To Teach General Chemistry Todd A. Hopkins* and Michael Samide Department of Chemistry, Butler University, Indianapolis, Indiana 46208, United States S Supporting Information *
ABSTRACT: This article describes an approach to general chemistry that involves teaching chemical concepts in the context of two thematic laboratory modules: environmental remediation and the fate of pharmaceuticals in the environment. These modules were designed based on active-learning pedagogies and involve multiple-week projects that dictate what content is taught and in which order the content is presented. Students were expected to design experimental procedures, analyze data, and communicate their results. A description of the two laboratory modules is included along with a week-by-week description of the student experience.
KEYWORDS: First-Year Undergraduate/General, Curriculum, Environmental Chemistry, Laboratory Instruction, Physical Chemistry, Inquiry-Based/Discovery Learning, Hands-On Learning/Manipulatives, Drugs/Pharmaceuticals, Precipitation/Solubility fforts to reform the curriculum and student experience in general chemistry have continued for decades.1−4 A previous reform effort suggested increasing the amount of novel experimentation and activity available to the student in both the lecture and laboratory.5 To meet these goals, it was suggested that institutions (1) rethink the course starting from a fresh perspective, (2) organize content around a small set of topics, and (3) organize the course around laboratory experiences.5 In addition, the NSF-sponsored New Traditions Consortium describes mechanisms for moving from a facultycentered approach toward a more student-centered approach.6 In the Consortium report, several recommendations are made that should provide a mechanism for change, including implementing team problem solving, thematic teaching, and lab-driven curriculum. These recommendations align with what cognitive science tells us about the way students learn. For example, thematic teaching is important because it allows the students to place knowledge within a conceptual framework.7 Efforts to teach chemistry in the context of “real-world” issues have been well documented, with recent examples including efforts at civic engagement (SENCER),8,9 using the origin of life,10 and interdisciplinarity.11 Other recommendations for improving general chemistry include using open-ended laboratories and an inquiry-based lab-driven curriculum.6 The benefits of using inquiry-based laboratory experiences in general chemistry have been detailed by a number of authors.12−15 There are also examples in the literature where the laboratory has been used as the centerpiece of the general chemistry curriculum.16 This includes an effort by Bopegedera in which introductory students progress from guided inquiry all the way to multiple-week open-ended
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© 2013 American Chemical Society and Division of Chemical Education, Inc.
research projects.17 These studies show that placing lab at the center of the general chemistry curriculum is beneficial to student attitudes as well as to conceptual learning.16,17 This article describes a thematic laboratory-centered curriculum to teach a second-semester general chemistry course that combines aspects of themes and inquiry-based laboratories. Rather than comprising a series of chapters in a textbook, the course is organized around thematic laboratory modules addressing the “real-world” topics of environmental remediation and the fate of pharmaceuticals in the environment. The topics were chosen because most students have some level of awareness of environmental issues before entering the class, and there is a strong connection between the topics and the general chemistry content. In spring 2011, the chemistry department offered five separate general chemistry sections taught by five different instructors. Two of the five sections implemented the thematic laboratory-centered curriculum in spring 2011, followed by one section of advanced general chemistry in fall 2011. The second implementation in spring 2012 expanded to four sections (out of six total) of the second-semester general chemistry. These three semesters included 250 students, most of whom are not chemistry majors, but rather prepharmacy, pre physician’s assistant, and premedical (biology major) students. Each semester included two thematic lab modules that each required five weeks of experimentation (one three-hour lab per week) with an additional one to two weeks of preproject introduction and discussion. All of the students involved in the implementations Published: August 9, 2013 1162
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Table 1. Example of Weekly Expectations for the Environmental Remediation Module Week
Class
1
6
Definitions of environmental remediation, concentration conversion (ppm−M), Ksp and equilibrium, initial self-reflection Continue Ksp discussion, review titrations, introduce Ka and Kb, weekly to-do list, and selfreflection Work on Ksp, Ka, and titrations, and making connections to project, to-do list, and selfreflection Introduce titration curves, continue equilibrium, continue to make connections to lab, to-do list, and self-reflection Work on putting all concepts together for data analysis and conclusions, introduction of intermolecular forces and/or Gibbs free energy, to-do lists, and self-reflection Review of all content from project, final discussion of data analysis
7
Exam over this module
2 3 4 5
Laboratory No lab Lab introduction (safety, disposal of unwanted chemicals, etc.), introduction to resources, introduction of flow map Experimental work begins Experimental work and troubleshooting Experimental work and troubleshooting Experimental work, troubleshooting, and work on lab writeups (first drafts) Final writeups due
required to use precipitation as their method of remediation, but the self-reflection rubric (see the Supporting Information) shows that the chemical content in this module (and the corresponding exam) focuses on solubility (Ksp), acid−base equilibrium (Ka, Kb), concentration, and titration. An example of week-to-week expectations is shown in Table 1, and a more detailed description of the implementation of this module is included in the next section.
of this curriculum had the same instructor in lab and lecture. The lecture sizes were typically 30−40 students with lab sizes of 15−20 students. Each laboratory module proceeds from a context-based (fictitious) scenario, which lists the assigned laboratory-based goal. Students work in groups (2−4) and are given multiple weeks to complete the task. In the laboratory, students are provided with a flow map that provides guidance in developing their procedure to address the goal. In the classroom, the scenario provides the basis for learning and discussing the underlying theory, content, and data manipulations. Instructors typically used combinations of lecture, problem-based learning, and group work in the classroom, but it is important to note that the thematic laboratory-centered curriculum should be adaptable to any classroom pedagogical approach. Throughout the multiple-week process, students complete weekly to-do lists and self-assessments to track their progress and learning.18 To complete the assigned task, the students collect, analyze, and evaluate their laboratory data, and communicate their results to the target audience specified in the scenario. Details of the implementation of each of the modules are described in the next sections. This includes a description of the module and a chronological description of the student experience in lecture and lab, along with concerns or issues that were identified in the first implementations. All of the student handouts for the lab modules are provided as Supporting Information. Data from standardized exam scores and student surveys are included to demonstrate that the students are learning the typical content expected of a second-semester general chemistry course through the thematic lab modules.
Implementation
In the first (1−2) weeks of the module, the students’ focus is on planning their laboratory projects and starting to learn the content required to plan effectively. Students start by researching topics, such as brownfields, maximum contaminant level (MCL), remediation methods, and the U.S. Environmental Protection Agency (EPA) and its regulatory role. These topics form the basis of discussion for important chemical content areas. For example, MCLs for metal ions are reported in mg/L (parts per million in the low concentration limit),19 and students have to learn to convert between molarity and ppm to plan their lab work. Students also discover that chemical precipitation is a method of remediation for metal ions, which leads to discussion of precipitation reagents based on Ksp values (along with the introduction of equilibrium). They also learn that they can use Le Chatelier’s principle to increase metal ion precipitation. Discussions also focus on how they will determine whether their demonstration project has been “successful”. This leads to an introduction to acid−base titrations, how indicators work, and how the changing pH during a titration can be used to signal an end point. The students are introduced to spectroscopic analysis, including atomic absorption and using Beer’s law for data analysis. At this point, the students have been introduced to content that spans 3−4 chapters in a typical general chemistry book. Throughout the rest of the module the students will learn to use these concepts in their experiments and data analysis. In this introductory phase, students begin their weekly to-do lists (see the Supporting Information) for the project. The todo list includes a section to list goals and accomplishments for lab work, content learning, and a self-reflection rubric. These to-do lists play two important roles in the projects: (1) student metacognition (ability to self-assess learning), which is an important factor in learning,7,20 and (2) communication between student and instructor. For example, faculty feedback on the action plans can help guide laboratory projects or steer students to helpful homework assignments. In addition, these assignments provide a constant reminder of the chemistry they are learning.
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ENVIRONMENTAL REMEDIATION MODULE The students start this lab module with an assignment (see the Supporting Information) based on a scenario where the local city government receives possession of a brownfield, and the city wants the retention pond on the property remediated before converting the land into a public park. Students, as employees of a remediation company, create and implement an experimental procedure that demonstrates their ability to remove metal ions from the pond. The students are also given a flow map (see the Supporting Information) that outlines the process of remediating metal contamination using chemical precipitation. This map allows students to visualize the overall process of experimentation and assists them in defining specific details related to the work (concentration of reagents, precipitation of the metal with hydroxide ion, standardization of the reagents by titration, centrifugation, and filtration to remove the metal salt from the system, etc.). Students are not 1163
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Table 2. Example of Weekly Expectations for the Fate of Pharmaceuticals Module Week
Class
1
Lewis structure review, line structures, introduction to buffers, initial todo list, and self-reflection Continue buffer discussion, introduce kinetics, weekly to-do list, and self-reflection Work on kinetics, introduce electrochemistry, make connections to project, to-do list, and self-reflection Continue kinetics and electrochemistry, continue to make connections to lab, to-do list, and self-reflection Work on putting all concepts together for data analysis and conclusions, to-do lists, and self-reflection Review of all content from project, final discussion of data analysis Exam over this module
2 3 4 5 6 7
Laboratory Introduction to lab and flow map, student research and short presentation on pharmaceutical contamination of environment Experimental work begins Experimental work and troubleshooting Experimental work and troubleshooting Experimental work and troubleshooting Experimental work, troubleshooting, and work on data sheet and PSA video Final data sheet and PSA video due
which is an open-ended assignment where students can write about what they learned, what they would do differently, or describe their group dynamics (e.g., how much everyone contributed).
In the next 4−5 weeks of the module, students complete their lab projects and written assignments. As most of the chemical content has already been introduced, class time is spent refining their understanding and learning how to use the content in developing and analyzing the data from their lab experiments. Content that is not directly related to their projects can be introduced. For example, intermolecular forces are introduced to help explain the solubility of their precipitant, or Gibbs free energy can be introduced to explain why reactions have a particular equilibrium constant, Ksp or Ka. Students continue to complete weekly to-do lists and self-reflections, which become more detailed as students gain a better understanding of their projects. As they begin their planned experimentation, most of the student groups choose metal hydroxides or metal carbonates for the precipitation process (procedure shown on flow map). Based on Le Chatelier’s principle, they choose to add an excess of the base, which can be titrated to determine the success of their remediation. The students make all of their own solutions, including their model “pond” and any precipitation reagents. They use acid−base titrations to standardize their precipitating reagents and HCl solutions to titrate the supernatant to determine their results. Many of the students complement their titrations with atomic absorption (AA) spectroscopy to confirm their results, which means that they have to make calibration standards for the AA. At this point many of the students encounter problems with their experiments, and troubleshooting these problems is an important part of the learning process. For example, some groups determine that their method removed 200% to 600% of the metal ions. This error is due mostly to improper concentrations or lack of precision in their titrations. Problem identification is followed by procedural modification, but the 4−5 weeks of lab work allows sufficient time to make and correct mistakes. For example, some student groups have completely switched metal ion contaminant or precipitating reagent or both while still completing the experiment on time. Student groups summarize their work in a two-page document. This document contains a background on remediation, a description of their method, data, and a discussion of their results. Students are expected to interpret and understand their data, draw conclusions about their work, and communicate the information. The audience for the documents is an interested and informed city government, but not necessarily chemistry experts. Therefore, students must describe the procedure, justify all of the steps, and explain the meaning of their results to this audience. At this point, individual students also write a final self-reflection document,
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FATE OF PHARMACEUTICALS IN THE ENVIRONMENT MODULE The students start this lab module with an assignment (see the Supporting Information) that states that a local environmental organization is starting a pharmaceutical recycling program. This organization requests help encouraging citizens to bring their unused and expired pharmaceuticals to the recycling sites. Students are asked to measure the rate of degradation of a model drug molecule under environmental conditions and use that information to generate a public service announcement (PSA) video to encourage use of the recycling sites. A partially filled flow map (see the Supporting Information) guides some of the questions students should ask, but does not specify a procedure. Because of their experience with the first module, students are expected to do more experimental design in this project, which focuses on kinetics (rate laws, mechanisms, temperature dependence), buffers, oxidation−reduction reactions, and electrochemistry. Table 2 provides an example of the weekly expectations, followed by a more detailed description in the text. Implementation
Because this comprises the second course module, students are given only one week of introduction without lab work. During this time, students are given an assignment (see the Supporting Information) to research the issue of pharmaceuticals in the environment, where students use governmental Web sites (EPA, USGS, etc.) to answer specific questions. The students then use this information to put together a short presentation (∼2 min) for class. This research provides the context of the problem of pharmaceuticals in the environment and helps the students formulate an experimental plan. Because most pharmaceuticals are represented as line structures, some class time is dedicated to reviewing these structures and their meaning, and how to draw them. As the students are choosing the drug molecule to study, the instructor can place parameters (based on availability, price, etc.) on the student choices, or even have everyone in the class study one particular drug. Because students do experiments at the pH of environmental waters, the concept of buffers is typically the first topic discussed in class. This also provides a “bridge” to the acid− base equilibria and reactions discussed in the previous project. At this point, students begin weekly to-do lists and self1164
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students engaged in a self-assessment process using SALG21 where they scored themselves on their preclass knowledge as well as the learning gains made during the course. Second, the students took the standardized second-semester general chemistry exam from the ACS exams institute. Because these measurement tools were not used in the general chemistry sections that followed a more traditional approach, there is no comparison data to determine if the laboratory-centered approach is “better” than a traditional approach. Results from the SALG survey of key content areas covered by the laboratory-centered curriculum are shown in Figure 1. In
reflection grids (see the Supporting Information) for this project. The first two weeks of laboratory work involve considerable preliminary experimentation as students explore the solubility of their pharmaceuticals, measure the detection limits of UV− vis spectroscopy, or conduct initial experiments on the degradation of the drug molecules. Students also typically use this time to make their buffer solutions, where they learn the distinct difference between calculating buffers and making them in the laboratory. Classroom discussions focus on learning chemical kinetics, rate laws, method of initial rates, and integrated rate laws. Because they are evaluating the rate of degradation of pharmaceuticals, students rely on the tools of chemical kinetics to analyze data and guide their experimentation. Electrochemistry and oxidation−reduction reactions are introduced in class discussions because students may choose to study the oxidative decomposition of their drugs (mimicking some natural processes). In fact many of the students try oxidative decomposition with hydrogen peroxide or bleach because they find that their chosen drug molecule degrades very slowly (or not at all) through hydrolysis. Students write their to-do lists and self-reflection grids to reinforce their learning and plan their projects. Over the last four to five weeks of this module, students are very active in lab trying to gather and analyze kinetic data on the breakdown of their drug molecules. These projects require troubleshooting to determine all of the experimental variables, including how often to measure the concentration using UV− vis and concentration of any added oxidizing agents. The students have to struggle with the fact that their data do not always fit to simple rate laws and rate-law analyses. As results become apparent, students spend some of their time in lab, especially between kinetics measurements, planning and scripting their PSA videos. In the classroom, the students get more comfortable with the mathematical manipulations of chemical kinetics, and discussions focus on comparing the kinetics rate data to the reaction mechanisms for some of the degradation pathways. For example, the students can compare the mechanism of acid-catalyzed hydrolysis of aspirin (acetylsalicylic acid) to the integrated rate law that they (or their classmates) have recorded in lab. The last portion of class is spent reviewing and integrating the concepts of kinetics, redox, and buffers with respect to their projects. Students complete their to-do lists and self-reflection grids up until the last week of the module. Finally, student groups are required to submit a one-page document describing their kinetics results. This document is similar to the data sheet for the environmental remediation module, which continues the idea of condensing 5 weeks of data into one succinct summary document. Students also submit their PSA video aimed at convincing the public to use a pharmaceutical recycling site, which should be an engaging, creative video that incorporates their kinetics data in the message. The students upload their videos to YouTube and send the link to the instructor. (This way the students get to decide how public or private their video is.) Once again, each student writes a one-page self-reflection document, which provides a last chance for metacognitive reflection about what was learned or what would be done differently.
Figure 1. Three-semester average for student assessed learning gains for five key content areas. Gray bars represent preclass assessment while black bars denote perceived learning gains at the end of the semester.
the preclass survey, the students claimed to have more knowledge (“somewhat” to “a lot”) of titrations, solubility, and acid−base equilibria content areas than for electrochemistry and kinetics. In the postclass survey, students reported good learning gains in all five key content areas. These student-perceived learning gains are consistent with the analysis of ACS standardized exam data. Figure 2 shows student performance on the exam broken down by content topic. This analysis shows that students did better on topics that were specifically covered in the two laboratory modules. For example, the students were better at questions related to kinetics, acid−base chemistry, and concentration than
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COURSE OUTCOMES To ensure that students were gaining exposure to key content areas, two different measurement tools were employed. First,
Figure 2. Three-semester average for ACS standardized exam performance, broken down by content area. IMF is intermolecular forces. 1165
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(15) Russell, C. B.; Weaver, G. C. Chem. Educ. Res. Pract. 2011, 12, 57−67. (16) Ricci, R. W.; Ditler, M. A. J. Chem. Educ. 1991, 68, 228−231. (17) Bopegedera, A. M. R. P. J. Chem. Educ. 2011, 88, 443−448. (18) Veal, W. R.; Taylor, D.; Rogers, A. L. J. Chem. Educ. 2009, 86, 393−398. (19) EPA National Primary Drinking Water Regulations. http:// water.epa.gov/drink/contaminants/index.cfm#List (accessed July 2013). (20) Cooper, M. M.; Sandi-Urena, S. J. Chem. Educ. 2009, 86, 240− 245. (21) Student Assessment of their Learning Gains (SALG) Home Page. www.salgsite.org (accessed July 2013).
colligative properties and nuclear (not related to laboratory projects). Overall, the student average on the ACS exam is comparable to the national average for the exam, 35.1 versus 36, respectively. These results show that the students are learning the typical content expected out of a second-semester general chemistry course.
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CONCLUSION In an effort to build on a movement to reform the general chemistry curriculum, we have developed a thematic laboratorycentered curriculum for second-semester general chemistry. Laboratory modules have been developed using themes based on environmental remediation and pharmaceuticals in the environment. In the laboratory, students plan and execute an experiment based on the theme of the module, and lecture class time is used to learn the underpinning chemical concepts. The students analyze, evaluate, and communicate their laboratory results in order to complete the projects.
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ASSOCIATED CONTENT
S Supporting Information *
Grading rubrics, course handouts, including the assignment sheet, laboratory flow map, to-do list templates, and examples of student work for the environmental remediation and fate of pharmaceuticals in the environment thematic laboratory modules. This material is available via the Internet at http:// pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors thank Jeremy Johnson and Tracy LeGreve for helping gather exam data for the course and for helpful comments throughout the implementation of the laboratorycentered approach to general chemistry. The authors also thank the students of CH107 and CH106 at Butler who participated in this thematic laboratory centered curriculum.
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REFERENCES
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