Bond polarity and molecular shape
A molecule is polar only if its polar bonds fail to cancel, which depends on its shape as much as its atoms.
A worked example
CCl4 has four polar C-Cl bonds, but the tetrahedral shape points them symmetrically outward so the dipoles cancel and the molecule is non-polar.
The mistake people actually make
Boiling a molecular substance breaks the forces between molecules, not the covalent bonds inside them. Polar bonds do not guarantee a polar molecule.