OMSI/WinterHaven PSD2000 Project:

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Inquiry Session 3: Watershed Chemistry

Return to OMSI's Chemistry Lab with the WinterHaven students to conduct advanced experiments in watershed chemistry.

Computerized pH Testing | Soil Testing | Environmental Chamber

Computerized pH Testing

WinterHaven students extended their understanding of previous Environmental Chemistry experiments by participating in a newly developed demonstration of advanced pH testing.

Refining the Acid Rain and Rock Bottoms experiments, OMSI Chemistry Lab educators showed students the advantages of measuring pH electronically using a pH probe hooked to a personal computer (PC).

Students discovered that the greater accuracy of an electronic pH probe could dramatically affect the results of an experiment with minute changes in pH that would not be apparent in the subtle color gradations of simple pH tests.

Helping students understand the difference sophisticated scientific tools can make, OMSI educators showed how a pH probe/PC system can allow scientists to model simple laboratory systems and then extend the information they obtain to the "real" world (like watersheds). Students learned that if scientists can match their models to real world conditions, they can make predictions regarding environmental impact and change.

Special thanks to Vernier Technologies for the contribution of OMSI's pH probe/PC system.

Soil Testing

With their new knowledge of advanced pH testing, WinterHaven students conducted a newly developed OMSI Chemlab experiment for testing soil.

Students were given three soil samples of unknown origin (soil taken from three separate locations around the Portland area) and asked to measure the pH of their "unknowns" both before and after a gardening additive (fertilizer) was mixed in. This experiment demonstrated that the soil in the Portland area is slightly to moderately acidic and how soil amendments can change soil pH.

The results of students' tests were interesting in that all the readings were fairly consistent and showed POSITIVE pH changes after adding fertilizer for two of the three unknowns (expected), but NEGATIVE changes for all groups testing the third unknown (unexpected). The positive change is expected due to the predominance of ammonium compounds in the fertilizer. But the negative change in the third sample suggested a very different soil compound that will require further analysis to explain.

Through this experiment, students encountered a scientific commonplace--unexpected results--and learned that the actual scientific process often requires changing or expanding an experiment to account for the unexpected.

In a final experiment, students mixed samples with moderately concentrated hydrochloric acid in the hopes of extracting various metals for detailed analysis. OMSI educators will complete more complex and dangerous tests for iron, copper, phosphorous, and heavy metals and return results to the students for analysis.

Students learned that constituents in the soil are directly tied to plant health and the well-being of a watershed: Too much contamination can lead to plant growth inhibition and the consequences of run-off and leaching (especially given the acidic nature of the soil) can be devastating.

Environmental Chamber

WinterHaven students were given a "sneak preview" of an experimental OMSI Chemlab demonstration: an environmental chamber. The chamber provides a miniature ecosystem to recreate and test environmental changes such as global warming, acid rain, erosion and soil leaching.

go back to Inquiry Session 2

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