Which of the following does not dissolve in water?

Nonpolar substances do not dissolve in water due to the nature of their molecular structure. Water is a polar molecule, meaning it has a slight positive charge on one end and a slight negative charge on the other. This polarity allows water molecules to form hydrogen bonds with other polar and ionic substances, effectively breaking them apart in solution.

In contrast, nonpolar substances lack this charge separation and do not interact favorably with water molecules. Since there is no attraction between the water molecules and the nonpolar substance, the nonpolar substance tends to remain separate from the water, leading to its insolubility in that medium. This is why oil, a classic example of a nonpolar substance, does not mix with water, instead forming a distinct layer.

Polluted water or fatty substances are good illustrations of nonpolar materials that will not integrate into aqueous solutions, further solidifying the distinction between polar and nonpolar interaction in biological and chemical contexts.