What are polar and non-polar molecules? Give their examples.

(N/A) Non-polar molecules: These are molecules in which the centers of positive and negative charges coincide,resulting in a net dipole moment of zero. Examples include $CO_{2}$ and $CH_{4}$. These molecules develop an induced dipole moment only when placed in an external electric field.
Polar molecules: These are molecules in which the centers of positive and negative charges do not coincide. Consequently,they possess a permanent electric dipole moment even in the absence of an external electric field. Examples include $H_{2}O$ and $HCl$.