Developed by:  Catherine R. Ney
Subject:  Physical Science
Unit:  Environmental Pollution
Grades:  Middle grades: 4-8

Pollution You Can and Can't Detect

Objectives:
 1. To use the senses to discover the presence of pollution.
 2. To discover that some pollution can not be detected using the senses alone.
 3. To discuss the hazards of undetectable pollutants.

Materials:
 unlabelled liquid containers:  water, 36 oz. container of rubbing alchohol, (food color half and leave half uncolored) and an 18 oz. container of bleach litmus paper (4-pieces per group) clear cups (4-per group)

Procedure:
 1. Read James H. Reece's Lester and Clyde, the simple story of the effects of pond pollution.
 2. Children work together in groups of four.  Groups fill each cup 1/3 full of unlabelled water. Label cups number 1, 2, 3, and 4.
 3. Next fill each cup 1/3 more with colored alchohol (cup 1), uncolored alchohol (cup 2), bleach (cup 3), and water (cup 4).  Predict liquids.
 4. Observe each cup by sight and smell.  Ask:  What observations can you make?  (The colored alchohol in cup 1 and the bleach in cup 3 can be detected)
 5. How can we find out what is in cup 2, and 4? (litmus test)  Students use litmus paper to detect the presence of uncolored alchohol in cup 2 and water in cup 4.

Discussion:
 1. Discuss pollutants. (Some pollution you can see or smell; some pollution can not be seen or smelled, but is present).
 2. What impact can undetected pollution have on the environment?

Evaluation:
 1.  Check groups results.
 2.  Assess students' notebooks for observation input.
 3.  Evaluate students' participation in discussions.