In case of all polar molecule the amount of inter molecular forces (such as cohesion, adhesion etc.) is much smaller than intramolecular forces (such as dipole –dipole interactions, Hydrogen bonding etc.)
Due to this reason a polar molecule form a dipole –dipole structure due to which the charges are unevenly distributed on different parts of neutral molecule. The electrons are more strongly oriented towards oxygen atom and thus it gets negatively charged and hydrogen gets positively charged. A polar molecule attract another polar molecule either through Hydrogen bonding or through dipolar attraction between them.
For example dissolution of HCl in water is a polar -polar molecule interaction.
Because it's partially permeable membrane so it won't let anything get inside the leaf so by this cuticle the leaf is protected not to let any foreign substances in and preventing loss of water
