In the Laboratory
A Multiweek, Problem-Based Laboratory Project Using Phytoremediation To Remove Copper from Soil General Chemistry Labs for Teaching Thermodynamics and Equilibrium Stephen G. Cessna,* Tara L. S. Kishbaugh, Douglas Graber Neufeld Departments of Biology and Chemistry, Eastern Mennonite University, Harrisonburg, VA 22802; *
[email protected] Gretchen A. Cessna Department of Chemistry, James Madison University, Harrisonburg, VA 22807
Gaining a clear conceptual understanding of foundational chemistry principles in thermodynamics and equilibrium early in college chemistry instruction is critical to successfully completing a four-year degree program in chemistry. Because thermodynamics and equilibrium undergird and permeate many principles taught in upper-level college chemistry courses, concept mastery of fundamentals scaffolds subsequent mastery in advanced chemistry and biochemistry topics (1). These principles also underlie science concepts in multiple disciplines (e.g., molecular and cellular biology, chemical engineering, and hydrogeology), and thus, being able to apply these concepts is important for success in several science professions (1–3). Despite the importance of learning thermodynamics and equilibrium concepts, many chemistry education researchers have demonstrated that it is remarkably difficult for students to learn them (4–8). These difficulties arise from at least three sources: (i) the very abstract nature of the concepts themselves (5–7); (ii) the prior (often misguided) knowledge that students bring into the classroom, which can be a hindrance to learning the concept in a manner that coincides with accepted scientific knowledge (4–7); and (iii) a common teaching style in college chemistry courses that emphasizes the manipulation of mathematical symbols and numerical calculations, often with little thought towards assuring that the students gain a qualitative and widely applicable understanding of the underlying fundamental concepts (6–8). Problem-Based Learning for College Chemistry One successful way to promote conceptual learning of difficult science concepts is to provide activities that fully engage students in learning, particularly teaching scientific concepts within a “real-world” context that relies on students’ using those concepts to solve a problem (2, 9–15). Thus, a problem-based laboratory project that explores introductory chemistry concepts in a relevant and authentic context might significantly assist other teaching efforts to improve students’ learning of such concepts. In fact, several reports in the chemistry education literature describe multiweek, problem-based research projects (14–19). The following two claims are generally made in these reports. First, little is lost in transitioning from teaching a series of disconnected, traditional laboratory exercises to teaching a multi-week problem-based project. Rather, all or most of the conceptual content and skills that need to be “covered” in the teaching laboratory still can be. However, some breadth of experience is sacrificed (i.e., introduction to several different laboratory techniques). Second, broader learning outcomes are more readily addressed in a multi-week authentic context than they can be in a more traditional lab setting. These outcomes include learning about the nature of science, the nature of scien726
tific research and scientific careers, critical and interdisciplinary thinking skills, group problem-solving skills, as well as affective outcomes (14–19). Based on the literature and our research interests in environmental analysis and remediation, we were excited to bring a multi-week laboratory project to the second semester of a first-year general chemistry course, centered on a research project in copper phytoremediation. Phytoremediation of Copper-Contaminated Soils— A Ten-Week Project for General Chemistry Phytoremediation, or the use of plants for the removal of toxic chemicals from soil or water, has received substantial research interest in recent years (20–23). Several plant species hyper-accumulate specific metal ions, thereby demonstrating an enhanced ability to reduce concentrations of these ions in the soil in which they grow. For example, Indian mustard (Brassica juncea) accumulates high levels of lead, cadmium, and copper when grown in soils contaminated with those metals (20). New plant species, new cultivars, and new genetically engineered plants are continuously being tested and developed to remediate soils contaminated by specific metal ions, in combination with specific planting regimes and microbiological and chemical soil amendments (20, 21). In this manner, significant advances have been made in the remediation of toxic levels of soil lead, selenium, mercury, arsenic, cadmium, zinc, cobalt, and copper (20–23). Because of its promise for restoring arable land and healthy ecosystems, phytoremediation has been considered an interdisciplinary “hot topic” at the interfaces of chemistry, ecology, botany, geology, and soil science (22, 23). Perhaps because phytoremediation is conceptually so accessible to beginning scientists and is also interdisciplinary and largely unexplored, three recently published papers describe problem-based chemistry laboratory projects revolving around a phytoremediation research context (17–19). Here we describe a similar laboratory project that we have introduced in a secondsemester general chemistry course taken by first-year science majors. We share the enthusiasm for using phytoremediationbased or other research projects in the early years of chemical training with the authors of these other papers(17–19). Unlike the projects described in those reports, our project is directed at the conceptual development of second-semester general chemistry thermodynamics concepts (equilibrium, enthalpy, entropy, Gibbs free energy) and analytical skills development, and is focused on phytoremediation of copper. Goals and Desired Learning Outcomes We fully revamped the laboratory portion of the secondsemester general chemistry course in Spring 2006. We have
Journal of Chemical Education • Vol. 86 No. 6 June 2009 • www.JCE.DivCHED.org • © Division of Chemical Education
In the Laboratory
now taught the revised course for three successive years. All of the students thus far enrolled in the course (35–45 per year;
