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Activity 8 - Water Quality - pH and Field trip #1

Water Quality - pH

Estimated Time of Activity: 45 minutes (2)

Goals: Process Skills and Content Knowledge:

  • Students will learn about the pH scale.
  • Students will measure and monitor pH of pond water.
  • Students will perform a series of scientific measurements and tests on wetland water.
  • Students will learn how to create a lab report.

Materials:

Activity Instructions:

  • Ask students to write what they think scientists look at when they study water and aquatic habitats?
  • List student responses on board.
  • Ask students: What would the information they collect tell them about water quality?
  • Introduce and discuss the water quality parameter – pH.
  • What is pH? The measure of acid content of water. It is the measure of H+ in solution. The more acidic a solution, the more H+ ions there are.
  • pH – scale → 0 – 14
    • Pure water has a pH of 7 (neutral)
    • pH below 7 → acid
    • pH above 7 → basic
  • How factors affect the pH level of water?
    • Vegetation type and density
      • Organic acids are naturally found in plants (sphagnum moss – bogs; several tree species). When they decay in the water : Decrease in pH.
      • When this material decomposes carbon dioxide is released. The carbon dioxide combines with water to form carbonic acid. Although this is a weak acid, large amounts of it will lower the pH.
    • Underlying strata of rocks and soil
      • One of the most important factors is the bedrock and soil composition through which the water moves, both in its bed and as groundwater. Some rock types such as limestone can, to an extent, neutralize the acid while others, such as granite, have virtually no effect on pH.
      • Limestone – increases the pH (basic)
    • Acid rain
      • Air pollution from automobiles and coal-burning utilities and factories
      • Sulfur Dioxide and nitrogen oxide are emitted from tailpipes and smoke stacks
      • When SO2 and NO2 combine with water in the atmosphere, they form sulfuric and nitric acids which fall to earth in the different forms of precipitation (?) This precipitation mixes with surface water in creeks, rivers, ponds and wetlands.
      • Acid rain is responsible for many of our first order streams becoming acidic. Serious problems can occur in spring when streams receive a massive acid dose as acidic snows melt.
    • Humans
      • dumping of chemicals into the water by individuals, industries, and communities. Remember - something as "harmless" as shampoo rinse water is actually a chemical brew and can affect the pH along with other chemical parameters of water.
      • Many industrial processes require water of exact pH readings and thus add chemicals to change the pH to meet their needs. After use, this altered pH water is discharged as an effluent, either directly into a body of water or through the local sewage treatment plant.
  • pH range preference
    • pH of natural systems under normal circumstances is typically between 6.0 and 8.0. This is the most favorable range for life, although some organisms can tolerate harsher conditions
    • Sudden, dramatic changes in pH could endanger the lives of young animals
    • Ask students- What is the pH of a healthy lake?
    • At what pH would fish die? Frog eggs, tadpoles, crayfish die? Is rainbow trout a fish that is sensitive to pH?
  • What are buffers?
    • Something that neutralizes acids and bases in a solution.
    • Chalk (calcium carbonate CaCO3), baking soda (NaHCO3) and antacids act as buffers. Mix these with lemon juice and vinegar and see the change in pH.
  • What are the different ways to measure the pH of water?
    • There are many ways to measure pH. These are the three frequently used test.
      • Hydroion paper – read the whole scale 0 – 14,
      • red and blue litmus paper –
        • red turns blue in presence of base – stays red in presence of base;
        •  blue turns red in presence of acid and remains blue in the presence of a base;
      •  pH meter – reads the amount of H+ ions in a solution.
  • Introduce the lab activity and lab report, going over the different parts.
  • Tell students the materials they are working with [pond water from different locations; litmus paper, test tabs, medicine dropper].
  • Have students form a hypothesis about the pH of the different pond water from different locations.
  • Have students create a procedure for them to test their hypothesis.
  • Have students create a chart to record their data.
  • Have students form a conclusion based on their data.
  • Create a class list of pH measurements.

Pre-Activity:

  • Do Now: Ask students to write what they think scientists look at when they study water and aquatic habitats? What would the information they collect tell them about water quality.

Assignments:

  • Complete lab report

Assessment:

  • Answers to student activity sheet.
  • Quality of lab report.

Testing pH of pond water – Field Trip #1

Estimated Time of Activity: 1.5 – 2 hrs

Goals: Process Skills and Content Knowledge:

  • Students will learn different methods for finding out about a study site.
  • Students will conduct a visual survey of study site to discover information about local land cover, water quality and document their findings.
  • Students will test the pH of the water found in a local park.

Materials:

  • Lamotte pH testing kit
  • Digital water quality meter
  • Digital cameras.
  • GPS
  • Water Walk Sheet

Activity Instructions:

  • Before students go on field trip, have them answer the three Pre-Activity questions on slips of paper.
    • Show/review students how to perform each water quality test they will perform in the field
  • At the Field Site: Tell students that before they perform tests at the field site, they must first perform a visual survey to discover information about the field site.
  • Hand out Water Walk Student Activity Sheet and give the students 15 -20 min to walk around the water body and complete the worksheet.
  • Hand out materials for pH testing (might be best to prepare ahead of time in plastic baggies for distribution to individual groups).
  • Have students’ record data in their appropriate data sheets.
  • Remind students to take pictures with their digital cameras of the field site and the act of performing the pH test.

Pre-Activity:

Collect permission slips from students.

Ask students:

  • Is there a lake, river, pond or stream that you visit?
  • What is your favorite thing to do at this place?
  • Why is this body of water important to you?

Go over the different parts of the Water Monitoring Form.

Start lab report for the days activities by asking students to hypothesize the pH of the water body that you will be testing. (Students should have researched this for last lessons H.W.)

Assignments:

  • Have students email pictures taken on today’s field trip – at least three of the field site and two of sampling.
  • Have students complete a lab report. Students should hand in a copy of the Water Monitoring Form per pair/team.

Assessment:

 Lab report

 

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