DONNABOGNER
Wichita State University Wichita. KS 67208
A New Approach to the Baking Soda-Vinegar Reaction G. Lynn Carlson
University of Wiswnsin-Parkside Box 2000 Kenasha. WI 53141 One reaction used t o illustrate chemical reactivity is the reaction between baking soda and vinegar. I t is safe, inexpensive, and provides strong visual reinforcement of the concept. However, the reaction can easily hecome passe, since it is used so often. Student interest can he reawakened, and additional concepts taught, if students themselves are used to represent the reacting atoms. The equation for the reaction of baking soda and vinegar is shown below. NaHC03 + HC,H,O,
-
NaC,H,O,
+ H,O + CO,
This exercise takes 14 students, one to represent each atom in the equation. Each student should write the symbol for h i s h e r element on color-coded construction paper-red for oxygens, black for carbons, yellow for hydrogens, and green for sodium. Then join students by hand (to show the bonds) in the individual starting compounds, connected to the correct adjacent atoms.
Na+ -WC-O-H
I
+
The ionic nature of sodium-carbonate bond can he indicated if the avvro~riate students stand next to each other .. . without joining hands: the other covalent bonds can then he revresented bv ioined hands. Now mix the two "chemicals" &d have them-rearrange into their products. Notice that Group A stays stuck together and merely trades a hydrogen for a sodium.
Group A This exercise can also illustrate conservation of matterthere were no atoms left over when the reaction was complete. For. more advanced students, the concept might he extended to illustrate the importance of balancing equations to avoid "ornhan" atoms. I t can also reinforce the idea that the hondinp'of individual atoms within a molecule follows a set of organized rules that can he learned. EdRor's Note:
One of the reviewem tested this method with her classes, then extended the technique to include the following ideas: (1) Illustrate the four general types of reactions. When students read about them in the text, they canvisualize having seen these reactions during a previous lesson. (2) the fact that in ionic reactions. one or mare -~roducts . . Em~hasize . leave the reaction medium as a solid.. Iiauid. . ~.or ..pas. IS) Reactiuna in which the coeffirienu are greater than 1 can be accomplished by drawing upon a pool of ionaor atom waiting to participate. ~~~
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Group A
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Volume 67
Number 7 July 1990
597
