Which of the following is an example of a polar molecule?

Water is an example of a polar molecule because it has a bent molecular shape and a significant difference in electronegativity between its atoms. In a water molecule (H₂O), the oxygen atom is more electronegative than the hydrogen atoms, which creates an unequal distribution of electron density. This results in a partial negative charge near the oxygen atom and a partial positive charge near the hydrogen atoms. As a consequence, water has a dipole moment, meaning it has distinct positive and negative ends, which is characteristic of polar molecules. This polarity allows water to form hydrogen bonds with other molecules, which is essential for many biological processes, including temperature regulation, solvation of ions, and nutrient transport in living organisms.

In contrast, oils are nonpolar due to their long hydrocarbon chains that do not have significant differences in electronegativity between the atoms; thus, they do not have distinct positive and negative ends. Metals typically form ionic or metallic bonds rather than molecular structures and do not exhibit polarity as defined in the same way. Gases may vary in polarity, but many are nonpolar or consist of single atoms, such as noble gases, which do not have any dipole moments.