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(Not in my drinking water!)



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Background / Context

Theme: Tap water quality/Lead Testing

Grades: 9-12 Chemistry/Physical Science


Urban students are seldom interested in anything that does not effect them directly. They can avoid the water in lakes and streams, however, they cannot avoid water which they consume. Water quality in Milwaukee is always an issue (remember cryptosporidium?). Once students perceive the need to investigate further, after exposure to information provided by teacher demonstration and media supported articles, they will test their own water samples and report their findings.

Description of School:

John Marshall International Baccalaureate High School is an urban public high school with 1500 students of diverse ethnic and socioeconomic backgrounds. The majority of the students are inner city minority youth. Marshall is culmination of 85 percent African American, 7 percent Caucasian, 3 percent Hispanic, and 5 percent Asian individuals. John Marshall High School reflects the diversity of its learners by offering a comprehensive program that includes a School to Work initiative, a broadcasting and technology specialty program, and the recently attained International Baccalaureate program for the college bound.

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Getting Your Feet Wet

Part A: The Diversion/Demonstration

The beginning of this unit starts in the classroom. At the beginning of class students are usually talking amongst themselves and need a diversion to direct their attention.

Ms. Wittig draws their attention by asking if anyone, and how many, would like something to drink. She then tells the students their order is coming right up and brings out pitchers of drinking water; all cold and delicious. She must also pour herself a glass and only drink half in their presence.(Make sure that the teacher's glass is a clear glass so that students can see the contents.) The remainder of the glass is to be used in the second part B. The students receive their refreshing drinks and are enjoying themselves when Ms.Wittig asks that anyone who wants seconds can raise his/her hand.

Part B: Activating Prior Knowledge

Ms.Wittig then brings out a pitcher of foul looking water that was hidden under the counter. (The water simply has sterilized sand floating in it which the teacher stirred up before it was brought to the surface.) She then encourages the students to have their second glass of water from the dirty pitcher. Students will obviously make noises of disgust; one might even hear a small chorus of, "Are you nuts?". The teacher then asks, "Why did you change your minds"? Students might reply, "That water looks nasty"! Ms. Wittig might then probes the class by asking, "What does the way water looks have to do with its quality"? A student might reply, "Water that we drink out of the faucet doesn't look like that; its clear". "Oh," Ms.Wittig replies, "I can fix that". Next a filter system created from an old two liter soda bottle is brought out. The teacher pours the water through the filter and captures the remaining effluent on the other end. (This may take a little time, so move on to part C)

Part C: Presenting a Discrepant Event

Ms.Wittig continues the conversation, "While we are waiting for the water to filter, let me ask you about this pitcher of water". Another pitcher of water is brought out from under the counter that appears to be the same as the water they drank; clear and cold. (This pitcher of water has been rigged with an impurity of dilute sodium hydroxide.) Ms.Wittig asks the students:

Responses from the class might include:

At this point Ms.Wittig directs the discussion:

Students may offer the following:

"Well, we could run that test", says Ms.Wittig, "but let me show you another test we haven't done yet". "Who has heard the term pH and can tell me what it means", she asks. If this topic hasn't been covered yet no one will be able to offer any answers. Ms. Wittig might then ask the following:

Students might reply:

After useful responses are offered Ms.Wittig explains what acids and bases and indicators are and then follows up with a demonstration. Three tall cylinders of clear liquid are placed on the counter; one labeled acid, one labeled water, and one labeled base. Into each cylinder 5 drops of universal indicator is placed; the contents are stirred with a glass rod and the students can see the colors created. Ms.Wittig asks a student to identify the label on each tube and describe the color present. Responses from the students should be:

"This is very similar to the rainbow isn't it", Ms.Wittig asks. "What color is in the middle of the rainbow", she asks. A student might reply, "Green is the color in the middle". "Good", Ms.Wittig responds, "now let's connect those thoughts to compare the rainbow to the colors of water in the tubes". "Tanesha, why would the color of water be green when the indicator is in it", Ms.Wittig asks. Tanesha guesses, "Because water is not an acid or a base". "That's it", responds the teacher, "and solutions that are neither acid nor base are considered to be neutral".

Ms. Wittig then holds up the third pitcher of water and asks the students again if they would drink water from this pitcher, yes or no, and why or why not. Once enough students are solicited she moves on to prove to the students that the water is not drinkable by using the universal indicator; the solution turns violet.

Part D: Tying Up Loose Ends

Ms.Wittig then summarize what has been learned so far and makes the following points:

At this point Ms.Wittig places her glass half full of water on the table next to the glass of the water captured by the filter system. The teacher ask what changes in the water do the students notice and if they think it is drinkable. Responses might be:

The teacher then puts a few drops of universal indicator in the effluent and the water turns green. The teacher then explains the set up.

The teacher wraps up the discussion with, "Here in this city we are fortunate, our water is filtered by the water department for the city. There are standards that must be met before the water can pass through the pipes to us. Recently, though, in Milwaukee many people got sick from drinking city water because of an organism called cryptosporidium. Remember, the people could not tell that the organism was in the water by site, taste, or smell; but, boy they sure felt the difference. Since then steps have been taken to screen more carefully for cryptosporidium. There is, however, another danger that is rarely talked about, but truly exists in this city; exposure to lead in drinking water. I would like you to read the following article and I would like you to come up with points to discuss tomorrow".

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Middle / Go With the Flow

Summarizing the Article

After reading the article on lead exposure, the class will be polled as to what points were made by the article. Students may offer the following points:

After these points are made Ms.Wittig asks the students, "What would you like to know about your drinking water"? A student is assigned to keep track of the questions on a transparency for later use. Some of the responses might be the following:

Students will be guided to concentrate on lead. The teacher might say, "Most bacterial forms are taken care of the article says, but remember, lead is one of those things that isn't tested for by the municipal water department". "What would you add to the list to find out about lead", asks the teacher. Students might respond:

Any other valid questions may be added to this list as necessary. The teacher then informs the students that he/she knows of a test to measure the amount of lead in water and asks if the students would like to test their water from home to see if it contains lead. The response is a favorable one, and so, the teacher moves forward to discuss the project.

Eliminating Variables

The students are responsible for designing the sampling process of water. The conditions under which the water is drawn must be the same for each student at home. The instructions for water sampling might include the following:

The teacher reminds the students that since water runs through pipes that they should take note as to the type of pipes they have in their home.

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Tapping Knowledge

Ms. Wittig has reserved the computer lab for the class on Monday, Wednesday, and Friday for six weeks. Mr. Everson will diligently monitor to see that the equipment is up and running properly so that students can utilize the computers to their fullest capacity.

In the computer lab students will be seen researching articles that have been linked into the project. They may also contact experts as needed via e-mail. Since there are a number of questions asked within each role more than one student will be working on the questions. The work will be evenly distributed within the group and the students will be seen asking one another for help and sharing ideas. Ms. Wittig circulates around the room checking to see if students are on task and giving guidence. Other schools have similar programs and can be contacted via the internet. Information that is gained or shared will be posted to our school web site which can be updated on a regular basis.

In the classroom, students are investigating qualitative analysis, ion formation, and ion detection. Students are introduced to the lab procedure and allowed to practice on stock solution samples. Ms.Wittig makes sure that safety procedures are followed and interacts with each student to assess whether or not they are comfortable with the procedure. Students are instructed to tap their home sources and bring them in for sampling.

When enough of the class is comfortable with the laboratory procedures, Ms.Wittig will assign a competent student to an insecure one. The students will run their tests, collect their data, and clean their area. The data will be posted to the web page.

Using the daily assignment sheets, Ms.Wittig can keep track of where the students have been and see if they are on track. She will often write personal notes to help guide the student in the right direction and give positive feedback on a daily basis. The students will be using these daily assignments as part of their notes. Granted, a journal may work just as well for students, but Ms.Wittig knows that she must stay on top of her students.

End / Culmination

In the sixth week of the project students will be presenting their information as an oral report at the town meeting. When the class has heard all of the information presented they must decide on which direction to go with the information. All of the tests will be done and the results posted.

If the concentration of lead in the drinking water at or above standard levels there are many options available. Students will want to share the information with their parents, as well as, what preventative measures they can take. Students will be encouraged to report their findings to the Department of Health and Human Services, or the Environmental Protection Agency. Or, students may come up with any other feasible plan to utilize the information. Ms.Wittig will be excited to hear what they choose to do.

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Created for the Fermilab LInC program sponsored by Fermi National Accelerator Laboratory Education Office and Friends of Fermilab, and funded by United States Department of Energy, Illinois State Board of Education, North Central Regional Technology in Education Consortium which is operated by North Central Regional Educational Laboratory (NCREL), and the National Science Foundation.

Author(s): Catherine Wittig and Todd Everson
School: John Marshall International Baccalaureate High School Milwaukee, Wisconsin
Created: March 1, 1999 - Updated: April 25, 1999