WHAT WATER WOULD YOU DRINK?

Barbara Liukkonen
Board of Water and Soil Resources
394 South Lake Avenue Room 403
Duluth, MN 55802

Level: Grades 4-6

 

Estimated Time Required

 

Anticipated Learning Outcomes

 

Background

This works well in an informal outdoor setting or in a classroom. It is a hands-on activity that fosters decision-making skills and emphasizes scientific principles such as objectivity and replication.

 

Materials

 

Procedures

A. Advance preparation

  1. Number the six 2-liter PET bottles from 1-6 and fill them with potable water. "Contaminate" five of the six bottles by adding several drops of food color, anise, onion extract, creamer, or salt. Leave the sixth bottle unpolluted. Four bottles should now appear clear, one will be reddish, and one should be cloudy. Sample the clear solutions to make sure they are concentrated enough for the students to smell or taste the contaminant, but not so concentrated that it is visible. When salt is added at high enough concentrations, it may make the water cloudy, so give it enough time to dissolve before beginning the activity.
  2. Number enough small paper cups so that each team will have one each of numbers 1-6. Partially fill the numbered cups with the corresponding "contaminated" water. Don't fill them too long in advance because the water gets warm and begins to taste like the paper cup.

B. For the activity

  1. Ask questions such as "What is pollution?" "Where does it come from?" "Are all contaminants from human activities or are some natural?" (Mud, algae or bacteria, iron, salt are common responses for natural pollution.) "What color is pollution?" "Does pollution make water unsafe for all activities?" (Boating, fishing, transportation, irrigation, swimming, drinking are activities that require different levels of water quality.) "What do we intentionally add to water before we use it?" (chlorine and fluoride).
  2. Explain that they are going to do an experiment to identify which of the water samples they would like to drink (or use at home). They are going to use three of their five senses. Review the five senses.
  3. Break the students into teams of four or five. Give each team 2 blindfolds, a clipboard and pencil, and a form for recording results. One student will be the recorder and one will run the experiment. One blindfolded student will taste and the other will smell the samples.
  4. As a group, have students look at the large bottles and select which they'd be willing to drink based only on their sense of sight. It's difficult to see what the sample really looks like in the small paper cup and this helps the group to understand how to carry out the experiment. Have the recorder write "yes" or "no" for each bottle in the SIGHT column. As the experiment progresses, she should ask the blindfolded students their opinion about each sample and then write "yes" or "no" for each sample under TASTE and SMELL.
  5. Explain that none of the water is unsafe, but that some doesn't taste good and they should only taste a sip. Also discuss how the students who can see should be careful not to influence or bias the blindfolded students' opinions by telling them what number or color the sample is, or by making comments about how gross it looks. Explain the concept of scientific objectivity.
  6. Remind students that those who are blindfolded will need help in passing the samples, but that they should be allowed to taste and smell by themselves!
  7. Have each team pick-up their six cups, blindfold the two who will taste and smell the samples, and let them carry out the experiment.
  8. After completing the experiment, students should decide which sample was the best overall based on sight, taste, and smell. In theory, they should have all yeses for the sample that didn't have anything added.

 

Results and Discussion

  1. As a group, have students hypothesize what was in each bottle and compare results.
  2. Discuss why they had different opinions and explain the concept of replication (repeating an experiment and comparing results).
  3. Summarize types and sources of natural and human-made pollution, those that present a health risk and those that affect the aesthetics of water.

 

Additional Activities

  1. A worksheet is available for use after the activity; it can be used immediately or after a week or two to measure retention of key concepts.
  2. Continue with activities, "How Much Water Is There?", "Is Dilution the Solution?", and/or "Water Words", all in this volume (but only one is on-line).

Worksheet Key: WHICH WATER WAS CONTAMINATED?

  1. What is contaminated or polluted water?
    Water that contains anything besides "pure" water; water with anything in it that we don't want; dirty, harmful, dangerous, toxic, colored, etc.
  2. List three contaminants that we can see.
    Junk or litter, dirt or sediment, color, algae blooms or weeds, oil
  3. List three contaminants that we can't see.
    Man-made chemicals, minerals, chlorine, germs or bacteria, pesticides
  4. T or F All contaminants are harmful to humans.
  5. T or F If water looks clear and pure it isn't contaminated.
  6. T or F Pollution we can't see can't hurt us.
  7. T or F Some contaminants that aren't toxic to humans may harm plants or other animals.
  8. T or F Water that smells bad is harmful to humans.
  9. What did you learn about water contamination during the field day?
    Answers will be something like: what looks bad doesn't necessarily taste or smell bad; bad tasting or smelling water may look good; our senses can deceive us when we try to categorize water quality; some contaminants have no taste, odor, or visible indicators, but they may be a health risk for us or other life forms.
  10. List three things that you can do to reduce water contamination.
    Don't litter; use less water; use chemicals carefully (lawn, garden, farming); recycle; dispose of household hazardous waste properly; don't pour used motor oil along driveways; etc.


NAME:____________________

 

WHICH WATER WAS CONTAMINATED?
Student Sheet



  1. What is contaminated or polluted water?
  2. List three contaminants that we can see.
  3. List three contaminants that we can't see.
  4. T or F All contaminants are harmful to humans.
  5. T or F If water looks clear and pure it isn't contaminated.
  6. T or F Pollution we can't see can't hurt us.
  7. T or F Some contaminants that aren't toxic to humans may harm plants or animals.
  8. T or F Water that smells bad is harmful to humans.
  9. What did you learn about water contamination during the field day?
  10. List three things that you can do to reduce water contamination.




NAME_______________________

 

WHAT WATER WOULD YOU DRINK?

   Sight  Smell  Taste
GLASS 1      

GLASS 2

 

      
GLASS 3      

GLASS 4

 

      
GLASS 5       
GLASS 6      

Which glass of water would you drink based on your senses of sight, smell, and taste?

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