Question

How do the following properties of a substance change with increasing intermolecular forces?

Surface tension __________ with increasing intermolecular forces

Melting point __________ with increasing intermolecular forces

Boiling point _______ with increasing intermolecular forces

(increases, decreases, does not change)

Answer 1

a) Surface tension increases with increasing intermolecular forces because Intermolecular forces present in surface of water are H- bonds and if H-bonds are disrupted, surface tension decreases.

b) Melting point increases with increasing intermolecular forces because stronger the intermolecular forces of attraction, more energy will be required to break these forces So more will be the melting point.

c) Boiling point increases with increasing intermolecular forces because greater will be the intermolecular forces, stronger will be the dipole- dipole interaction causes a powerful attraction between molecules hence more energy is needed to break them so boiling point also increases but vapour pressure decreases.