This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl[subscript 2] (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl[subscript 2] both collapse the swollen polymer gels. The gel contracted by NaCl reswells in deionized water, but that contracted by CaCl[subscript 2] does not reswell. The CaCl[subscript 2] contracted gel is subsequently immersed in concentrated NaCl solution to reverse the ion exchange. The Ca[superscript 2+] ions in the contracted gel are released, and Na[superscript +] ions are redistributed in the polymer network. The ion-exchange cycle is accomplished and the water-absorbing ability of the gel is recovered. Other compound pairs of monovalent versus polyvalent metal ions involving LiCl, NaCl, KCl, CaCl[subscript 2], BaCl[subscript 2], and ZnCl[subscript 2] give similar results. (Contains 1 figure, 1 scheme and 7 notes.)