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Author - Dale Moore - Summer 1997

Abstract: A desk-top chemistry demonstration is performed; students are asked to develop a Theory of Chemical Combination by evaluating several metaphorical mod6ls, then propose experiments to test the predictions each model makes.

Reading/Texts: Optimally, coverage of Ziman through Chapter 2 with no additional assignment. The activity is meant to reinforce sections 2.5 and 2.8 in the text, especially the use of metaphor in constructing theories and prediction in testing them.

Description of Case Materials Samples of components A (aqueous cobalt solution; pink), B (ammonia in water; colorless), C (ethylenediamine in water; colorless), D (acetone; colorless -- CALJTION: Flammable, volatile, will dissolve nail polish and similar lacquer), and E (hydrochloric acid; colorless -- CALTTION: Corrosive, fumes, wash immediately after use), all in vials with droppers; at least five test tubes; a test tube rack; a wash bottle; a waste jar; paper towels for mess; materials can be obtained from the Cheriu'stry Department stockroom. (Call Dale Moore at ext. 2754 to verify avallablility.)

Case Use The materials above are combined to cause a series of color changes in test tubes. From the demonstration, the students are asked to develop a "Theory of Chemical Combination." Each student group is given a metaphor to use to develop their theory, and asked to devise experiments to test their theory. After a work period, the different models are compared and the class is asked to reach a consensus on the theories.

References:

• General introductory text for chemistry in Library; can check with Chemistry Department for sample texts to review. - (none are in the library.
• Snyder, Carl H. The Extraordinary Chemist[y of Ordinary Things, 2nd Ed., John Wiley & Sons, Inc.: New York, NY, 1995. { Macon--Stacks, 3rd floor QD33 .S69 }