Answer to Question #340291 in General Chemistry for denden

Question

Water spreads out on a glass surface but beads up on a waxed surface. Explain the difference.

Answer 1

In this particular case, following observation might be explained with the use of adhesive forces of compounds. Adhesive forces between the molecules of glass and water are stronger than the cohesive forces between the water molecules. For this reason, water can spread on the glass surface. On the other hand, adhesive forces between the molecules of wax (named paraffin which is non-polar) and water are weaker than cohesive forces between the water molecules. Because of this, water forms small beads on a glass surface polished by paraffin.