Days Needed: 2-3
Materials:
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-empty 2-liter soda bottles, one for every two students
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-fish tank filter charcoal, rinsed
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-pebbles
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-sand
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-nylon stockings, cut into 2 inch squares
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-rubber bands
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-tall empty plastic cups, two for each pair of students
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-one cup measuring cups
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-substances to filter, such as: food coloring, cooking oil, dish soap, dirt
Day One: Making Filters
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step 1—cut bottoms off of soda bottles
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step 2—wrap a piece of nylon stocking over top of bottle and secure with rubber band
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step 3—put one cup each of pebbles, sand, and charcoal in that order, in the bottle as shown in the picture.
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step 4—place bottle in empty plastic cup to stand
(figure available in print form)
Day Two- Filtering (This may take more than one day)
TEACHER NOTE: Before class, organize material to be filtered. Mix oil and water 1/2 and 1/2, mix dish soap and water 1/2 and 1/2, mix dirt and water to make water very cloudy, and mix enough food coloring with water to make the color very dark.
Once filter is used, it is difficult to clean and reuse because the pollutants stay in the filter. I suggest that each group be given one substance to filter and each group may then report its findings to the class.
Procedure:
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Step 1: The substance our group has is:___________________________
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Step 2: Measure substance to be filtered and record the amount. Record the amount:
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Step 3: Record on your lab sheet your observations on the substance to be filtered. Be exact about what you see.
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Step 4: Be sure the empty cup is under your filter to catch the liquid which comes out. CAREFULLY pour your substance into the filter. Write down any observations you make on how the substance flows through the filter.
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Step 5: Once the liquid has run out of the filter, record what the liquid looks like, note particularly how the liquid compares to how the liquid looked before filtering.
Measure the liquid. Was any lost in the filtering process? If yes, then how much?
Questions
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1) Do you think that this filter did a good job cleaning the pollutant out of the water? Explain your answer in sentence form.
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2) What might make this filter more effective?
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3) In a water treatment plant, the filtering process is only one part of the treatment process. Before water is filtered, it is mixed with coagulant, sort of like jello, which attract the impurities in the water. The water is then run through filters, much like the filters we built. How do you think the coagulant helps the filtering process?
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____
*The coagulant form clumps which collect the impurities and are more easily filtered out.
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4) After water is filtered in a treatment plant it is treated with chemicals which kill any bacteria remaining in the water. Why is it that the filter is unable to remove the bacteria from the water?
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____
*The bacteria is microscopic, and seeps through the filter with the water.