How do polor molecules differ from nonpolor molecules?

A bond between two atoms is polar if the electrons of the bond are unevenly distributed. If the bond is polar enough the possibility exists for one atom to take both electrons. If it does that the bond breaks and it is said to have 'dissociated'. In general, solvents are referred to as polar and non-polar. Water (H2O) is a polar solvent while Acetone (Propanone) is a non-polar solvent. Water will dissolve ionic species such as salts, while Acetone will dissolve covalent (non-ionising) compounds.