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Critical Thinking in Science

Part 4: Water Quality


Students will study water quality and the effect of common pollutants while practicing their critical thinking skills in an inquiry based experiment. Students should focus on their local water source, however, materials are provided for the Falls Lake, Raleigh, NC water source. This lesson is written using the 5E Learning Model.

Learning Outcomes:

  • Students will evaluate the quality of various water samples.
  • Students will evaluate the effect of common pollutants on the quality of water.
  • Students will research the impact of human activities on the presence of pollutants in their own water source and the impact of the pollution.
  • Students will increase their inquiry skills.

Curriculum Alignment:

1.01 Identify and create questions and hypotheses that can be answered through scientific investigations.

1.02 Develop appropriate experimental procedures for:

  • Given questions.
  • Student generated questions.

1.04 Analyze variables in scientific investigations:

  • Identify dependent and independent.
  • Use of a control.
  • Manipulate.
  • Describe relationships between.
  • Define operationally.

1.05 Analyze evidence to:

  • Explain observations.
  • Make inferences and predictions.
  • Develop the relationship between evidence and explanation.

1.06 Use mathematics to gather, organize, and present quantitative data resulting from scientific investigations:

  • Measurement.
  • Analysis of data.
  • Graphing.
  • Prediction models.

1.08 Use oral and written language to:

  • Communicate findings.
  • Defend conclusions of scientific investigations.
  • Describe strengths and weaknesses of claims, arguments, and/or data

3.02 Explain the structure of the hydrosphere including:

  • Water distribution on earth.
  • Local river basin.
  • Local water availability.

3.04 Describe how terrestrial and aquatic food webs are interconnected.

3.05 Analyze hydrospheric data over time to predict the health of a water system including:

  • Temperature.
  • Dissolved oxygen.
  • pH.
  • Nitrates.
  • Turbidity.
  • Bio-indicators.

3.06 Evaluate technologies and information systems used to monitor the hydrosphere.

3.07 Describe how humans affect the quality of water:

  • Point and non-point sources of water pollution in North Carolina.
  • Possible effects of excess nutrients in North Carolina waters.
  • Economic trade-offs.
  • Local water issues.

3.08 Recognize that the good health of environments and organisms requires:

  • Monitoring of the hydrosphere.
  • Water quality standards.
  • Methods of water treatment.
  • Maintaining safe water quality.
  • Stewardship.

Classroom Time Required:

Materials Needed:


  • You will need to purchase test kits to find the pH, nitrites, phosphates, and chloride in the water. This can be purchased through scientific suppliers and aquarium stores.
  • Create a Procedure sheet for each lab station that has the directions for each test.
  • Bottled water, tap water, distilled water, outdoor water
  • Distilled water mixed with fertilizer, soap, roadside soil sample, and an agricultural soil sample
  • Copies of Water Quality Testing Lab


  • Experimental Design Graphic Organizer Water Version copies
  • Water Source Map Outline copies X3 per student
  • Water Map Activities Worksheet copies


  • Materials for student project choice

Technology Resources:

  • Overhead Projector

Pre-Activities/ Activities:

Engage: Water Pollution Discussion

Use the following example to begin the discussion of water pollution:

Kurt Vonnegut’s 1963 book “Cat’s Cradle” introduced a “new chemical” called ice-nine. Ice-nine is a different form of water that is solid at room temperature. Ice-nine trains regular water molecules to also be a solid at room temperature. When a single crystal is introduced into water, the water almost instantly becomes ice-nine as well. What would happen if ice-nine was introduced into our water?

Introduce this idea to the students and chose one of the following activities to help them engage in the topic:

  • Write a paragraph describing what would happen if ice-nine was placed into our water (Falls Lake for instance).
  • As a class, discuss what would happen to all of the water on the planet if ice-nine was introduced.
  • What would happen to living things because of this?
  • The discussion in number 2/3 can also be turned into small group discussions.
  • After students have discussed the effects of ice-nine, ask them to compare ice-nine to other pollutants that we add to water. What would happen if we destroyed our water systems like ice-nine?

Explore: Experimenting with pH, concentration, and volume (Time: 55 minutes)

  • Students will complete a Water Quality lab to first study the differences between tap, bottled, and outdoor water samples and second the affects of soaps, fertilizers, and basic chemical products on water quality.
  • Students will use the Water Quality Testing Worksheet (See Worksheet 1) to complete the lab.
  • Make sure the directions for these tests are available for the students at their lab stations. You can type one combined direction sheet for the tests and place it at each lab station.

Explain: Water Quality Follow up

Complete the lab questions. The questions focus on analyzing the data and relating the information to their own lives.

Elaborate: Our Water: Water Monitoring Plan

  • The students will create a water monitoring plan for their local water source.
  • All materials are provided for Falls Lake, Raleigh, NC. These should be adjusted for your local water source. Students will need an outlined map of their water source. The Falls Lake map is provided (See Worksheet 2).
  • Students should first complete the Map Activities Worksheet (See Worksheet 3) and complete the required map for each part.
  • The students should then discuss the “Before you Begin” questions with their group and determine the focus of their water monitoring plan.
  • The students will then complete the Experimental Design Graphic Organizer (See Worksheet 4) which has been slightly adjusted for this particular activity.
  • Finally, the students will write a water monitoring plan using their design.

Evaluate: Our Water Quality

Students should be allowed to choose and complete one of the following:

  • Create a poster about how to protect their local water source.
  • Create a brochure on how to protect their local water source.
  • Any other creative way to present what they have learned about water quality.
  • A sample rubric (See Worksheet 5) based on content, depth, accuracy, graphics, and neatness is provided. Adjust as needed.


Student’s Water Monitoring Plan should demonstrate their ability to design an experiment using information gathered in the Water Quality Testing Lab. Students should be able to move beyond simply testing the water and be able to organize the location, frequency, depth and other factors that will affect their water source. Review student’s graphic organizer and plan for consideration of these factors.

The evaluation section serves as an overall assessment of the student’s knowledge of water quality.


  • EDGO can be edited for any motor skill deficiencies by making it larger, or making it available to be typed on.
  • If there is a water source, stream, or river near the school visit and involve it in the lesson.
  • All basic modifications can be used for these activities.

Critical Vocabulary:

  • Water Quality
  • Water Pollution
  • Runoff


This lesson is part of the Critical Thinking in Science Unit and relies on the inquiry skills and vocabulary practiced in the first two lessons (Introduction to Experimental Design and How important is a decimal place?). This lesson should be used while teaching Goal 3 of the North Carolina Standards of Learning (water). Because students are using their local water source as a basis for the monitoring plan it helps them understand the importance of water health and safety. In addition, students are designing their own experiments to improve their ability to approach problems and questions scientifically. By developing their ability to reason through problems they are becoming critical thinkers.