The student will explain how filters work to remove substances from water.
(PA Science & Technology Standards: 3.8.7B; PA Environment & Ecology Standards: 4.1.7E, 4.3.7A)
The student will demonstrate how the variable of filter size relates to filtering effectiveness.
(PA Science & Technology Standards: 3.1.7B, 3.8.7A, 3.8.7C; PA Environment & Ecology Standards: 4.8.7C)
The student will conduct an experiment using the scientific inquiry process.
(PA Science & Technology Standards: 3.2.7B, 3.2.7C, 3.7.10B)
Observing, Inferring, Predicting, Measuring, Interpreting Data, Formulating Hypotheses, Experimenting, Solving Problems
Water with large and small suspended solids (prepared by teacher)
Various filters, as determined by students
Worksheet: "Data Table on Filter Effectiveness"
90 minutes over two days (20-30 minutes on day 1; 60-70 minutes on day 2)
1. Direct students to do exploratory research to develop a working answer to the question, "Where does water come from?" In addition to textbooks and other print resource material, students should consult relevant Internet web sites such as the following:
2. Have students share the results of their preliminary research. Ask students to suggest possible answers to the question, "How does water get to be clean enough to drink?"
3. Using student responses or guiding questions, lead students to consider the possibility of using natural and/or man-made filtering systems or devices to purify water. Have students brainstorm examples of filters they have encountered in their daily lives. (Teacher Note: Students will brainstorm possible household items that can be used as filters. Suggested filters may include but are not limited to: coffee filters, cloth, wire mesh, gravel, sand, and diatomacious earth).
4. Organize students into pairs or small groups. Tell each group to consult the following web sites for additional suggestions of filtering materials and/or devices. Direct each group to bring five potentially useful filters to class with them the next day.
5. On day two, give each group a bucket of dirty water and a turbidity meter. Ask each group to propose a process for filtering out the particulate matter in their bucket of water. Students should design a process using each of the filtering materials and/or devices they have brought from home.
6. Direct students to divide the water in their bucket into five samples and use one of the filters on each sample. Students will use the turbidity meter to check water clarity on each sample. Direct students to record the results of their testing on the "Data Table on Filter Effectiveness."
7. After completing the activity, have students groups orally summarize the filters they used and which ones worked the best to reduce the amount of particulate matter.
8. As a closure activity, ask the students if they would be willing to drink the water they just filtered (They should say NO!) Ask them to predict one or more additional steps that are needed to further clean the water to make it suitable for drinking.
Response on Activity Sheet: How Good is Your Filter?
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