Why do molecules with dipole-dipole force have higher melting and boiling points than molecules that only exhibit London Dispersion force?

Because dipole - dipole force is stronger than london dispersion force

Explanation:

Intermolecular forces determines a wide range of physical properties of matter of which melting point is one of them.

Both london dispersion forces and dipole- dipole forces are vanderwaals force.

But diople - dipole forces exists between polar molecules which are molecules with permanent dipoles.

In london dispersion forces the dipole is temporary

lol idk man i guess u gotta ask bill nye the science guy

the dissolution of polymer can be thermodynamically described in 2 steps.