If the molecules of two different substances have a similar size but the molecules of one substance are polar while the molecules of the other substance are nonpolar, what is most likely true about the substances?

For molecules of similar size, the main difference in their attractions is that polar molecules experience dipole–dipole forces, while nonpolar molecules generally have only weaker dispersion forces. The stronger attractions in the polar substance take more energy to overcome, so it usually has a higher boiling point. Therefore, the nonpolar substance has the lower boiling point.

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