Which statement best describes a polar molecule?

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.

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.