Summary

In this lab, students use simple pool test strips to collect water samples from local water sources, such as area faucets, pools, lakes, rivers, puddles, etc. They will compile all of the collected data to allow students to collectively make observations and ask testable questions. After determining a question of interest, groups of students will organize the related data, research relevant background information, form reasonable conclusions, and present their arguments.

Grade Level

High School and Middle School

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

• MS-ESS3-3: Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.
• HS-LS2-7: Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
• Scientific and Engineering Practices:
  • Asking Questions and Defining Problems
  • Analyzing and Interpreting Data
  • Planning and Carrying Out Investigations
  • Engaging in Argument from Evidence
  • Obtaining, Evaluating, and Communicating Information

Objectives

By the end of this lab, students should be able to:

• Experimentally determine the relative level of select ions in a water sample.
• Logically organize and analyze data on a spreadsheet.
• Interpret data to form a hypothesis.
• Suggest further investigation possibilities to related to a testable question.
• Use evidence to support or refute a claim.

Chemistry Topics

This lab supports students’ understanding of:

• Identifying an Unknown
• Solutions
• Ion Concentration
• pH Scale

Time

Teacher Preparation: 20 min (organizing materials, collecting information for students)
Lesson: 120-180 minutes (depending on how much outside of class work is expected)

Materials

• Any common pool test strip (minimum of 3 per student)
  • (Example: Pool and Spa Test Strips - Quick and Accurate Pool Test Strips )
• Plastic Test Tube or another collection tool (minimum of 3 per student)
• Large paper map of school district area/region (1 per group of students)
• Access to Google Forms/Sheets or other means to collect, compile and organize data

Safety

• Students should only collect water samples from safe water supplies (make sure students are aware of wildlife, hazard, etc.)
• Gloves are not necessary during collection but can be used to increase authenticity.

Teacher Notes

• The different portions of this lab can be completed over several days, at the teacher’s discretion, as time allows. Ideally, the pre-lab and reading portion can be completed on day 1, or outside of class, followed by the data collection also occurring outside of class. Students can compile results and analyze data and trends together in class while also formulating a testable question on day 2. Finally on day 3 for students to share/present results and discuss findings.
• To begin, explain how to use test strips to your students. Use the school tap water as an example and follow the instructions on the test strip package. Be sure to have students observe how the strips react over time and determine a standard for how and when to read results for your students to follow.
• The teacher should set up a system for students to record and compile results. Ideally, it’s suggested that the results are inputted into a form that can be easily transformed into a spreadsheet, such as a Google Form. Alternatively, results from a class can be compiled on a whiteboard or poster paper.
• The level of contamination will vary between locations, and research will need to be done on a school-by-school basis to determine reasonable background information.
• Reference articles should be provided for students related to each type of contaminant (halogens, metals, nitrates, or others) being tested to allow students to formulate reasonable claims.
  • Example articles:
  • Chlorination of Drinking Water (Washington State Department of Health)
  • The Top Heavy Metals You Should be Testing Water for (Brelje & Race Laboratories)
  • Drinking Water Nitrate and Human Health (National Library of Medicine)
  • Lead in Your Water: Is Any Amount Safe? (ChemMatters Magazine)
• Students will take 2-3 sampling kits home (strips and test tubes) and collect samples, documenting their source and location. See the images below for reference:

• Once students have collected data, the teacher should compile data into a spreadsheet to be shared with the class.
• Students should make observations and select questions to be investigated. Group students based on what questions they are interested in answering as it will facilitate more rich conversations to not have groups repeat the same questions. For example, students might see a trend in data related to chloride and decide to investigate the chloride content in wells versus municipal water.
• Depending on student comfort, walk students through how to organize data to represent a generic question being asked. Each group of students will design their own sheet, using data from the class data, but only need to include data relevant to their questions. For example, if students are investigating chloride content in wells versus municipal water, they would sort the spreadsheet to group well water data and municipal water data and ignore all of the data related to other tests such as metals, polyatomic ions, a particular water source, etc.
• After students have organized their data within their groups, have them discuss results and find a representative way to summarize the data. For example, this may be facilitated by using maps of your school district/region (to analyze any correlation between locations of collected samples), a variety of sticky notes, markers, etc.
• Finally, students should present their results/posters to the class. Groups can generate discussions after each presentation by proposing other related questions.
• Culminate with a discussion of possible errors in the class data collection, general conclusions, and/or possible next steps.