This laboratory project involves conducting chemical analyses of lake water and relating the results to the functioning of a lake ecosystem. Placing analytical work in a local context helps students understand how their laboratory activities relate to the "real world." In addition, students are asked to develop a good understanding of some of the many factors that affect a complex system; in this case a small lake.

The Chemistry "Big Idea" we are working with is analytical techniques are important for assessing water quality. The Sustainability "Big Ideas" are water quality and systems thinking.

This project is appropriate for the second or third quarter of General Chemistry for science and engineering majors. The lab assignments are designed to introduce students to chemical analyses in an environmental context. The lab activities include the tests listed below:

1. dissolved oxygen via redox titration
2. alkalinity via acid-base titration
3. calcium concentration via atomic absorption
4. phosphate concentration via colorimetry
   

After completing these analyses, students write a formal lab report on one of these topics, in which they present their findings using the format for a scientific paper. Within their paper, they are also asked to show a well-developed understanding of how their chosen topic relates to one of the other topics and how both topics relate to the ecosystem of a lake.

Possible Use in Other Courses

Portions of this activity might work in other settings and disciplines. For many of the tests included, simpler analytical methods are available (such as Hach test-kits.) Collecting data from these test kits and using that data as a starting point for understanding systems thinking would be appropriate in a variety of introductory science courses.

Timeframe

This activity is designed for four two-hour lab periods, with additional time needed for writing the formal lab report. This series of activities comprises about half of the lab time in a ten-week quarter.

The Learning Activities

Set-up: Prior to implementing this series of activities, it is helpful if students have some laboratory experience in chemistry. In addition, since the lake is so close to our campus buildings, we normally spend one lab day on a field trip to the lake to collect samples and to talk about environmental sampling.

Main Learning Activities: This project encompasses four lab activities (and an optional field trip to the lake) as well as a scientific paper. Each lab assignment includes some background information about how the focus of that lab relates to the lake ecosystem.

The "Lab Directions for Students" are: Dissolved Oxygen; Determination of Calcium using Atomic Absorption Spectrophotometry; Analysis of Phosphorus in Water by Spectrophotometry; Alkalinity.

Assignments: Students are asked to turn in lab data and analyses on a weekly basis. The formal lab report is due approximately two weeks after the laboratory analyses are completed. A copy of the information provided to students for their research paper is included as formal lab report (writing assignment for students).


Lab Reports: Environmental Sampling of Lake Waughop (Microsoft Word 41kB Nov8 11)
Dissolved Oxygen (Microsoft Word 43kB Nov8 11)
Analysis of Phosphorus in Water by Spectrophotometry (Microsoft Word 156kB Nov8 11)
Determination of Cacium Using Atomic Absorption Spectrophotometry (Microsoft Word 102kB Nov10 11)
Alkalinity (Microsoft Word 45kB Nov8 11)

For many students enrolled in General Chemistry, this is their first opportunity to write a scientific paper. Prior to writing this paper, students are provided with a fairly accessible example of a scientific paper to read. They are asked to pay particular attention to format, information included in each section of the paper, use of language, reference citations as well as data tables and graphs. The goal of this assignment is to help them become familiar with the style and content of a paper, rather than asking them to understand all of the scientific details of the paper itself.

During class, time is spent discussing the format of scientific papers. Students are also provided with a hand-out that describes the format of a scientific paper. (See attachment in Description and Teaching Materials section.) To provide students with an opportunity to read some of the scientific literature, they are asked to include specific citations to research articles within the Introduction section of their papers.

Some class time is also devoted to a discussion of some of the components of a lake ecosystem and how these components interact. This helps set the stage for each student's analysis of how their chosen topic (one of the four lab activities) interacts with one of the other lab topics.
Although we make use of a lake that is adjacent to campus, it would certainly be possible to conduct this set of laboratory activities using any number of different water sources. It could also be extended to incorporate outflow from a sewage treatment facility or other point source. Another option would be to compare a variety of commercially available bottled waters.

As this series of labs is currently conducted, the quality of student data varies widely. In particular, many students find it difficult to collect compelling data during the phosphate lab. Expanding each of the lab activities to more than one lab period would allow students to become more proficient at the techniques and more able to produce consistent results.

It would be interesting to collect student data over time to look for trends in the data.

The Chemistry "Big Idea" we are working with is analytical techniques are important for assessing water quality. A student's ability in this area will be assessed by evaluating the data gathered. A student's interpretation of their data will be assessed by evaluating their graphs and their answers to a variety of post-lab questions.

The Sustainability "Big Ideas" are water quality and systems thinking. A student's understanding of this idea will be assessed by evaluating how well they can express their understanding of the interplay between a different factors working within a system (as shown in their scientific paper.)

The primary resource that supports this activity is easy access to a fresh-water ecosystem. We also have fairly easy access to a salt-water ecosystem so some of the labs (such as alkalinity) compare values from fresh water systems and salt water systems.

We also have a small amount of historical data on the uses of the land surrounding Lake Waughop to help provide perspective.

To help students prepare to write a scientific paper, each student is given a published paper and asked to "dissect" it to become familiar with the format of scientific papers (as opposed to understanding all of the scientific details being presented in the paper.)