what is the diffrence between polar and non polar substances

Depending on the relative electronegativities of the two atoms sharing electrons, there may be partial transfer of electron density from one atom to the other. When the electronegativities are not equal, electrons are not shared equally and partial ionic charges develop.

The greater the electronegativity difference, the more ionic the bond is. Bonds that are partly ionic are called polar covalent bonds and substances which contains polar bond are called polar substances

Nonpolar covalent bonds arise when the electronegativities of the two atoms are equal.Substances which contains non-polar bond are called non polar substances.