What happens to these physical properties as the strength of intermolecular forces increases?

The Boiling point,melting point, surface tension and viscousity will increase while the Vapor pressure will decrease.

Explanation:An increase in the strength of intermolecular forces increases will lead to an increase in force applied to break the barriers posed by the strength of the molecules.

This increased intermolecular strength will cause a rise in boiling point,melting point, viscousity and surface tension.

The Vapor pressure reduces with increasing intermolecular strength. Vapor pressure is the amount of vapor that is equilibrium with its own liquid or solid. Hence,with increasing intermolecular strength the amount of vapor that is in equilibrium with its own liquid will reduce.