2. Water Analysis - Lesson Plan
- Introduce students to the idea of water quality testing. Water testing allows students to get a snapshot of the health of a body of water. Today's lesson is an opportunity to learn how to conduct these tests and interpret their results. These skills will be used later on in the course to examine water samples from terraqua columns and/or local water sources.
- Introduce each of the 3 tests and give a description of what each test measures and how each test is performed. You may want to quickly demonstrate each test using tap water as an example as you explain the procedure. Ask students for predictions of what differences one might expect between water samples?
- Specify the organization of the student's lab notebook and decide how data should be recorded at each station.
- Divide the students into groups and specify the rotation strategy. Rotate through the 3 stations, giving students 5-10 minutes per station. Allow time for a thorough clean up at the end of each station.
- Engage the students in a discussion of the differences between the water samples at each station. One way to do this would be to create a summary of all the students' results from each test on the board or on an overhead. Students can offer observations and comparisons for each test to add to the summarized results at the front of the room. Some examples of questions to ask:
- Were you surprised by any of the results?
- What do differences in temperature mean?
- What natural and man-made events might cause differences in temperature at a creek or lake? (depth, shade, velocity, altitude)
- What do differences in pH mean?
- What might cause pH differences?
- How should we interpret differences in dissolved oxygen?
- What conditions would increase or decrease dissolved oxygen?
- Would plant life increase or decrease dissolved oxygen? How about rotting plant life?
- How would differences in temperature/pH/dissolved oxygen affect the types of plants or animals that could survive in that water?
- How do different variables affect one another? For instance, how does temperature relate to dissolved oxygen?
- Did everyone get the same results? Why or why not?
- Armed with a thorough analysis of these water samples, begin a discussion of what makes water "healthy". Challenge students to decide what ranges of values for the various tests would be "healthiest"? and what range of values would be "unhealthy"?. This question is very open-ended and does not have a right or wrong answer but is an excellent way to generate discussion and delve deeply into the issue of water quality. One way to conduct this discussion is to allow students time to speak with their group about the question first, then share the group's conclusion with the rest of the class. A key factor to bring up is whether "healthy"? water is the same regardless of its location or use (such as a creek, pond, lake, bay or ocean).
- An alternative to the discussion of healthy water is to discuss the human activities that can affect water quality, both in good and bad ways. Challenge students to come up with a human impact (for example, pollution) and think about how that impact would change temperature, pH, and dissolved oxygen. Some possible impacts to consider include:
- Acid rain
- Invasive species such as elodea (commonly found in fish tanks but which can rapidly cover the entire surface of a pond)
- Wastewater treatment
- Planting trees
- Fishing and recreation
Submitted by irene on Wed, 2005-07-20 10:14