In the Laboratory
The Water Project: A Multi-Week Laboratory Project for Undergraduate Analytical Chemistry
W
Randy J. Arnold† Department of Biology and Chemistry, Huntingdon College, Montgomery, AL 36106;
[email protected] Anyone who has taught quantitative chemical analysis at the undergraduate level recognizes the need for innovative, hands-on laboratory experiences that will provide a greater challenge to students than the standard mix, measure, and report exercises. However, at the same time, the important lessons of following and recording experimental details, properly calibrating equipment, and performing statistical analysis should not be overlooked. At Huntingdon College, a five-week water project has replaced some of the lab exercises previously used in the CHEM 321 Analytical–Environmental Chemistry course. The project’s goals were to increase student interest, independence, and critical thinking skills while reinforcing the concepts and skills learned in the seven experiments performed on a weekly basis earlier in the semester. One of the biggest problems with standard laboratory exercises is that many students are not challenged to think independently. The students are usually required to complete a very specific list of tasks, which does not require them to think about what they are doing, while they are doing it. In many undergraduate chemistry labs, one of two scenarios generally exists. In one scenario, students execute the lab, report their results, and draw conclusions, all in the same lab period. While this plan may enable them to acquire important laboratory skills and prevents them from sharing one another’s ideas (cheating), it does not encourage students to reflect upon and understand one of the most critical concepts in analytical chemistry—the analytical process. Students need to learn to ask important questions regarding their experiment, such as why use this method and not another, what results do I expect to obtain, and what systematic errors are inherent to a particular method. Labs that last less than three hours from starting the experiment to writing the report do not allow time for such questions to be asked. In a second scenario, students execute the lab during the weekly meeting time and submit a report at the next lab meeting. While this method does provide ample time for reflection, it can lead to erroneous conclusions because students are expected to independently grasp concepts that may have only been recently introduced to them. A better approach would challenge students to think independently about a problem, while the instructor is readily available for consultation. A project-based laboratory (1–3) achieves these objectives while generally avoiding the pitfalls of the other laboratory teaching methods. Perhaps the largest obstacle to developing a multi-week project to incorporate into an analytical chemistry course is capturing student interest. Since clean drinking water is inherently important to everyone (even college students), it was expected that a water project would keep the students inter† Current address: Department of Chemistry, Indiana University, Bloomington, IN 47405
58
ested in their contribution to the project. Similar projects involving water analysis have been undertaken elsewhere (4– 6). Choosing water as the sample matrix also enabled the incorporation of well-understood testing methods and maximum contaminant levels, which the students had little or no difficulty finding. Water samples are also readily available. Drinking-water samples were obtained from campus buildings and natural-water samples were taken from rivers and the Atlantic Ocean. Since water quality depends on a large list of chemical compositions, unique chemical species were quickly obtained for each of nine students with no overlaps in the class. Analysis kits are readily available for measuring a large number of water contaminants. In most cases, these kits provided each student with one of their two methods of analysis. Method Each student chose one chemical species to analyze and two methods for measuring its concentration in each of the river, ocean, and drinking water samples. The chemical species and analytical methods used by the students are listed in Table 1. A LaMotte Smart Spectro spectrophotometer (7) and a number of reagent testing kits were used for several absorbance methods and one titration method. Each student was limited to 500 mL of HPLC grade water for standard preparation and dilution and to 25-mL samples of river and ocean water. Table 1. Chemical Species and Analytical Methods Used in the Water Project Chemical Species
Analytical Method
Calcium hardness
Titration (8, 9)
Chlorine, chloride
Spectrophotometry (10), ion-selective electrode (11)
Chromium
Spectrophotometry (10), atomic absorption (12)
Copper
Spectrophotometry (10), atomic absorption (12)
Fluoride
Spectrophotometry (10), ion-selective electrode (13)
Hydrogen ion
Titration (14), ion-selective electrode (15)
Iron
Spectrophotometry (10), atomic absorption (12)
Nitrate
Spectrophotometry (10), ion-selective electrode (16)
Phosphate
Spectrophotometry (10), titration (17)
Journal of Chemical Education • Vol. 80 No. 1 January 2003 • JChemEd.chem.wisc.edu
In the Laboratory
Prior to beginning the water project, the students completed seven laboratory exercises, each lasting one week. These exercises covered a variety of topics including volumetric glassware calibration, indicators, gravimetric analysis, weak acid titration using a pH electrode, EDTA titration, spectrophotometric analysis, and ion-selective electrodes. Each laboratory exercise included one lab period in the chemistry lab and a second period during the same week that convened in a computer laboratory. In the chemistry lab, students completed the procedure and recorded the data in their laboratory notebooks. In the computer lab, students used spreadsheet software to analyze their data and determine their results. Students submitted their laboratory notebooks as their reports for each lab. Students were not allowed to take their notebooks with them or use them outside the laboratory periods. During the first four weeks of the water project, students were given the choice of spending their laboratory time either searching for information, performing experiments in the lab, or processing their data. Students generally spent the first week of the water project reviewing procedures, finding standard chemicals, and calculating how to prepare their standards. Most students completed their measurements in the second and third weeks of the project. By the fourth week, all students were preparing calibration curves from their data. The fifth week was spent preparing and giving their presentations. At the conclusion of the project, students submitted a written report detailing their procedure, calibration curves, results, and, where applicable, a statistical comparison of the
two methods. The students also presented their results in a public forum open to the campus and larger community, where they explained the significance of their chemical species and displayed their calibration curves and results with uncertainties. The students used PowerPoint 2000 (Microsoft Corp.) software for the presentation. Once all components of the project were complete and final reports had been submitted, graded, and returned, the students were surveyed regarding their impressions of the water project. Hazards Owing to the variable nature of a project such as this one, where students choose different methods of analysis, it is difficult to assess all of the hazards that may be encountered. Water samples are normally nonhazardous, but a number of the reagents, such as organic indicators, are potential health hazards, and other reagents are irritants. Students were educated about handling chemicals and safety information was available. Eye protection was always used. Survey Results Based on student survey responses from all nine students enrolled in the course (Table 2), even though most students (8 of 9) considered the water project challenging (question 1) and more time consuming than other lab assignments (question 2), they generally agreed (7 of 9) that the project was more interesting than typical chemistry lab assignments
Table 2. Sur vey Responses Strongly Agree
Agree
Neutral
Disagree
Strongly Disagree
1. I was challenged by the water project portion of this course.
2 (22%)
6 (67%)
1 (11%)
0
0
2. The water project was more time consuming than other laboratory assignments.
7 (78%)
1 (11%)
1 (11%)
0
0
3. I needed to use critical thinking skills to complete the water project.
3 (33%)
6 (67%)
0
0
0
4. Prior laboratory assignments in this course helped prepare me for the water project.
2 (22%)
6 (67%)
0
1 (11%)
0
5. The water project was more interesting than typical chemistry laboratory assignments.
3 (33%)
4 (44%)
2 (22%)
0
0
6. I enjoyed working independently during the water project.
3 (33%)
3 (33%)
3 (33%)
0
0
7. I discussed chemistry with other students during the water project more than during other laboratory assignments in this course.
1 (11%)
1 (11%)
5 (56%)
2 (22%)
0
8. All parts of the water project went as planned for me.a
0
1.5 (17%)
1 (11%)
5.5 (61%)
1 (11%)
9. I was surprised by some of the results I obtained during the water project.
1 (11%)
3 (33%)
5 (56%)
0
0
10. I would recommend continuing the water project as part of this course in the future.
1 (11%)
7 (78%)
1 (11%)
0
0
Questions
a
One student responded that part of the project went as planned while another part did not.
JChemEd.chem.wisc.edu • Vol. 80 No. 1 January 2003 • Journal of Chemical Education
59
In the Laboratory
Samples need to be treated for biological degradation so more accurate results can be obtained.
an enrollment larger than about twelve students. This recommendation assumes that students do not work in groups but work independently, which offers many benefits and was enjoyed by students, but might be compromised with negligible negative impact in order to accommodate a larger enrollment. Based on student response after the initial trial of the water project in the CHEM 321 course, our chemistry faculty are very encouraged by the project’s success and hope to incorporate the water project and similar projects into this and other laboratory courses in the future when appropriate.
It was time consuming, but I learned a lot from it. It's a great project to make students learn to work independently.
Acknowledgments
Table 3. Student Comments from Sur veys I learned a lot of new things. (smiling face) The project was very helpful in cementing analytical procedure in my mind.
The water project gave me an opportunity to apply the Analytical Chemistry that I have learned.
(question 5). From the instructor’s perspective, it is significant to note the students unanimously agreed that they need to use critical thinking skills in the project (question 3). Eight of nine students also indicated that prior laboratory assignments in the course helped prepare them for the water project (question 4). This response suggests that the prior lab assignments do serve a useful purpose. For the instructor, these week-long lab exercises are simpler to manage and allow the instructor to emphasize, and apparently convey, specific skills to the students. The structure of the project required students to work independently, which most of them (6 of 9) enjoyed (question 6). As with any investigative chemistry problem, not all parts of the water project went as planned (question 8), a valuable lesson for the students. While the students did not feel that they discussed chemistry more with their classmates (only 2 of 9) during the water project (question 7), the instructor noted a substantial increase in instructor-student interaction. A few of the students (4 of 9) even reported that they were surprised by some of their results (question 9). All written comments about the water project (Table 3) were positive and one even suggested an improvement in sampling technique. An overwhelming majority (8 of 9) of the students recommended continuing the water project as part of the course in the future (question 10).
The author acknowledges Huntingdon College for financial support of the project. The author acknowledges chemistry program colleagues Massimo Bezoari and Maureen Murphy for support and advice in implementing the project and reviewing the manuscript. The author acknowledges the students who worked so hard during the project, J. Bettis, A. Davie, S. E. Leverette, R. Moore, W. Morris, III, L. Nesbitt, J. Pinkerton, N. Ragan, and W. Scheer. The author also thanks Jane Williams, Director of Institutional Research and Effectiveness, for help in constructing the survey. W
Supplemental Material
Instructions for the students and notes for the instructor are available in this issue of JCE Online. Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.
Conclusions Students responded very favorably to the water project experience. The project was, in the opinion of the students and the instructor, both challenging and time consuming. The project achieved its educational objectives of requiring students to think critically and work independently. Many students detected abnormal levels of analyte in some or all of their samples. These students were forced to think about the possible reasons for such results. Were these results due to environmental or experimental factors? In regard to institutional support, the project required purchasing a number of new supplies, but not considerably more than would have been used in the laboratory exercises it replaced. Demand on the instructor for instruction and guidance greatly increased during the water project. This factor is both a cost in instructor time and a benefit in increased instructor–student interaction. Based on instructor availability and current laboratory equipment with nine students enrolled in the course, it would be difficult to attempt such a project with 60
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Journal of Chemical Education • Vol. 80 No. 1 January 2003 • JChemEd.chem.wisc.edu
