Suppression Exam 2 Practice

Affinity for water comes from polarity. Water is a polar molecule that forms strong hydrogen bonds with other polar species. Polar solvents have permanent dipoles and often possess groups that can donate or accept hydrogen bonds. When a polar solvent is mixed with water, favorable interactions form between the water molecules and the solvent molecules, replacing some water–water interactions and making the mixture energetically stable. This leads to miscibility, meaning the substances mix thoroughly to form a single phase. Examples include alcohols like methanol or ethanol and other polar solvents like acetone.

Nonpolar hydrocarbons lack dipoles and hydrogen-bonding capability, so they don’t interact favorably with water and tend to separate. Gases dissolve in water only to limited extents and aren’t inherently a group that “mixes with” water in the same broad sense. Water itself is already polar, so the general group that has an affinity for water or mixes with water is the polar solvents.