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Geochemistry All Around Us

Andrew Knudsen
,
Lawrence University
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Summary

We look at a variety of natural waters in and around Appleton over the course of the term. The goal is for students to recognize differences and how those play into the topics we have covered in the course.

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Context

Audience

I have used this exercise in our undergraduate geochemistry course, though with some minor tweaking it could be used at a variety of levels.

Skills and concepts that students must have mastered

By the time this activity starts we have covered general thermodynamics, including equilibrium, dissolution/precipitation, etc.

How the activity is situated in the course

This activity is part of a term long sequence of activities looking at water samples in the area.

Goals

Content/concepts goals for this activity

The main content/concept goal of this exercise is to help students understand equilibrium thermodynamics. My goal is to help them understand the connection between the numbers/equations/reactions we put up in class and what "really" happens.

Higher order thinking skills goals for this activity

The two big thinking goals for this project are data analysis and formulation of a hypotheses. Students are faced with real data that they collected, in many cases for the first time. They are then forced to understand why those numbers look the way they do, and, figure out if their numbers make sense.

Other skills goals for this activity

At this point I have not had students using much in terms of analytical equipment, though in the future I am planning on having them run samples on our AA. Additionally, students work in groups as they collect data. By the end of the term, I serve as little more than a taxi service as I expect them to be ready to take the lead on sampling. Finally, they are expected to put together a formal write up at the end of the term, which for many of them is the first time they are expected to write up their own data.

Description of the activity/assignment

This activity is actually a series of labs/field trip exercises I ran with my advanced geochemistry class a year ago. For this class, we went on a number of field trips to sample a number of local waters, including, High Cliff State Park, where the Niagran Escarpment is present, a local wetland reserve, Lake Winnebago, the Fox River (downstream from Lake Winnebago), and finally a nearby cave in the dolostone of the Niagran Escarpment. We tested these waters for a few relatively straightforward properties: hardness, alkalinity, pH, and dissolved oxygen. In the future I am going to expand these analyses to include analysis on our AA, and possibly sending samples away for ICP analysis on a suite of elements. These sampling trips followed our course materials looking at the thermodynamics of mineral solubility and the interaction of water with the atmosphere. Students were able to easily recognize how these waters were different, and were able to make reasonable hypotheses to explain these differences. Furthermore, because this was the first time I had sampled these waters (this was in my first year), I didn't know the answer, so students were themselves forced to determine whether their results were reasonable or not. As an additional note, I should credit Tony Hoch, my predecessor here at LU. Much of the material I used in these labs evolved from labs he had run while at LU.

Determining whether students have met the goals

At this point, my evaluation is done through simply grading their preliminary lab reports and then their final write-up.

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