Trends in Melting & Boiling Points

What will the main factor that determines boiling point of a substance be?

The strength of the induced dipole-dipole forces, unless the molecule can form hydrogen bonds.

What happens if you have 2 molecules with a similar number of electrons?

The strength of their induced dipole-dipole interactions will be similar.

What if 1 of the substances has molecules that are more polar than the other?

It will have stronger permanent dipole-dipole interactions and so a higher boiling point.

Summarise the trends in boiling points

The strength of induced dipole-dipole interactions determine the boiling point, unless they form hydrogen bonds, if 2 molecules have similar number of electrons then the strength of induced dipole-dipole interactions will be similar and so if 1 of the substances has molecules that are more polar, it’ll have stronger permanent dipole-dipole interactions and a higher boiling point.