- -. .- - -,. RON DELORENZO Middle Georgia College Cochran. Georgia 31014
An Analogy for Solubility: Marbles and Magnets Richard A. Kjonaas Indiana State University Terre Haute, IN 47809
For several years, I have been using an analogy, which I call the "Marhles and Magnets Analogy," to help students grasp some of the principles that are traditionally included in a discussion of solubility. Imagine a beaker partially filled with magnets and another partially filled with marbles. Now pour one into the other and stir.'l'he two will not mix.'l'heattrnction between the magnets prevents the marbles from becoming interspersed (dissolved) in the magnets. It also prevents the magnets from lenving each other and hecoming interspersed in the marbles. This part of
the analogy might he followed by a demonstration such as the addition of bexane to water and a discussion of molecular and ionic attractions. Now imagine a heaker of red marbles and a heaker of hlue marbles. When comhined and stirred they become completely interspersed in each other much like molecules of two nonpolar compounds such as hexane and octane. Finally, consider a beaker of red magnets poured into a heaker of hlue magnets. When stirred, they become completely interspersed much like an ionic or polar solute dissolving in a polar solvent. This analogy has been used effectively at both the high school and college freshman level. Because of friction. red magnets and blue magnew may not hecome interspersed as easily in real liie as they dn in the imagination. It is, of course, important to emphasize to the c l a ~ tshat molecular and ionic attractions are not magnetic.
Volume 61 Number 9 September 1984
765
