Which statement best describes a polar molecule?

• A. Molecule with partial charges. Mixes with water.
• B. Molecule with no partial charges; does not mix with water.
• C. A molecule that is always negatively charged.
• D. A molecule with a net zero charge but no partial charges.

Answer: (A)

Polarity comes from uneven sharing of electrons, which creates partial charges on different parts of a molecule. Those partial charges establish a dipole moment, so one end is slightly negative while another is slightly positive. This makes polar molecules interact strongly with water, a highly polar solvent, through dipole–dipole attractions and hydrogen bonding. So a description that a molecule has partial charges and can mix with water captures the essential feature of a polar molecule. The other statements miss this nuance: a molecule with no partial charges tends to be nonpolar and doesn’t mix as readily with water; a molecule that is always negatively charged would imply a full, not partial, charge distribution; and a molecule with a net zero charge but no partial charges would also be nonpolar, lacking the uneven electron distribution that defines polarity.