What is the difference between a polar molecule and polar bond?
A polar bond is one where the charge distribution between the two atoms in the bond is unequal. A polar molecule is one where the charge distribution around the molecule is not symmetric. It results from having polar bonds and also a molecular structure where the bond polarities do not cancel. For example, water has polar bonds and its bent geometry means that there is a non-zero dipole moment. On the other hand, carbon dioxide has two polar carbon–oxygen bonds, but they are such that the polarities cancel out, so there is zero dipole moment.