Title Page | Preface | Close This Window
«« Table of Contents | Next Page (Downloads) »

What Can We Learn about Water?

Students practice performing water-quality tests in the classroom prior to their creek monitoring experience.

Time required: 2 - hours Location: classroom Suggested group size: all students Subject(s): chemistry, environmental science Concept(s) covered: water quality monitoring and testing Written by: Tricia Corsetti, Tomales Middle School Last updated: 07/01/00

Student Outcomes
At the end of this activity, the students will be able to:

• Measure and monitor water samples in the classroom (pH, dissolved oxygen, and temperature).



• Draw conclusions about water samples and water analysis.

California Science Standard Links (grades 6 – 8)
This activity is linked to the California Science Standards in the following areas:

6th grade:

7b - appropriate tools and technology to perform tests, collect data, and display data;

7th grade:

7a - appropriate tools and technology to perform tests, collect data, and display data;

8th grade:

75e - determine pH of a solution.

National Science Standard Links (grades 5 – 8)
This activity is linked to the National Science Standards in the following areas:

• Content Standard A - Abilities necessary to do scientific inquiry.



• Content Standard B - Properties and changes of properties in matter.



• Content Standard E - Understanding about science and technology.

Materials
To be provided by the teacher:

• pH paper, small jars or cups, vinegar, milk, lemon juice, tap water, distilled water, soda pop, chalk, baking soda, aspirin, antacid tablets, safety goggles
• aquarium thermometers
• dissolved-oxygen test kit (if available), safety goggles, clear jars

Vocabulary
acid, alkaline, anaxic, base, dissolved oxyben, pH

Procedures

1. Set up each water-test station as follows:
   pH: Set up jars with some common substances (lemon juice, vinegar, rainwater, baking soda, and others . . .). Have available small cups for mixing and pH paper to perform test.
   Temperature: Set up several jars with hot, warm, cold, and ice-cold water. Have a thermometer available. If possible, set up two jars with the same temperature under a light bulb, one with a shield for shade, and one without.
   Dissolved oxygen: Set up a variety of liquid samples to be tested. You may choose samples from pH station or samples with dirt, soap, etc. Follow instructions on test kit.



2. Provide students with handouts
   Each student should have a field journal sheet for Water Data Analysis Information and The pH Scale. These sheets will be incorporated into their journals and travel with them on their field trip.



3. Explain water tests
   Stress that water testing will only give a ÒsnapshotÓ of creek health. Explain each station and what each measures. Students may record what each station measures on the Water Data Analysis Information activity sheet. Divide students into small groups to practice performing the tests with teacher supervision.



4. pH test directions
   Place pH paper halfway into the liquid for about 5 seconds, pull out, and notice the color the paper becomes. Dissolve the solid substances in distilled water and have students test them as well (chalk, aspirin, antacid pills). pH results will be recorded below pH scale on activity sheet in section marked "Common Liquids". Students can draw lines from liquid to corresponding pH rating.
   
   * A buffer is something that neutralizes acids and bases in solution. Chalk, baking soda and antacids act as buffers. Mix them with the lemon juice and vinegar and test the solutions again. Do not mix anything with ammonia!!! Some acid-base mixtures can produce dangerous reactions.



5. Temperature test directions
   Have students practice using the thermometers to get accurate readings. Students should compare their results to assess general accuracy.



6. Dissolved-oxygen test directions If you have access to a dissolved-oxygen test kit, the students will need to follow the directions carefully with your assistance. You will test a half-full container of water, then shake the container vigorously, and retest.
   
   Water left uncovered in a refrigerator or ice chest for 24 hours will have 10–11 ppm (parts per million). Water left uncovered at room temperature for 24 hours will have 8 ppm, and boiled water will have 1Ð2 ppm because the dissolved gases have diffused.



7. Class discussion
   Lead a class discussion about the procedures for accurate testing in the field and emphasize water safety procedures. Students may record additional information from this discussion on the Water Data Analysis Information field journal sheet.
   
   pH:
   What type of activities or events could impact pH?
   
   Why do highly acidic or highly basic conditions kill fish? Salmon eggs will die if rain becomes slightly acidic. What would make the rain acidic?
   
   Why might mayflies and caddisflies be able to tolerate more acidic water conditions than salmon eggs? Could natural conditions, such as the type of bedrock below the creek, affect the pH reading?
   
   Temperature/ dissolved oxygen:
   What is the relationship between dissolved oxygen and temperature?
   
   Why does the shaken water sample have more dissolved oxygen?
   
   What natural events could increase water temperatures?
   
   What human interventions could increase water temperatures?
   
   Is there a relationship between temperature and depth in the oceans? In creeks?
   
   Does water temperature affect the rate of photosynthesis by aquatic plants?
   
   Does water temperature influence the sensitivity of creek life to toxic wastes, parasites, and disease?
   
   What conditions would increase or decrease dissolved oxygen?
   
   Would rotting plants increase or decrease the dissolved oxygen?
   
   General:
   What are some of the limiting factors in an aquatic ecosystem? In a human community?

Extension ideas

1. Have students bring in several different water samples from the community and from around the schoolyard to test. Be sure to label each sample and record results.



2. Have students generate all the ways humans can impact water quality and the results of certain tests.



3. Investigate other parameters of water quality, including chlorine levels, nitrates, phosphates, conductivity, coliform content or level, and turbidity. What tests are used for measuring these parameters? What are the natural readings versus the danger readings for each of these? What are the possible sources and remedies?



4. Using a long sheet of paper, draw a river. Cut the paper into as many sections as you have students or teams. In addition, give each student a kind of land use. Have students illustrate their land use on their piece of "River Front Property." Then reconnect the river. Discuss how different land uses impact water quality and note that what happens upstream will effect the downstream.

«« Table of Contents | Top of Page | Next Page (Downloads) »