Understanding Boiling Point: A Comprehensive Guide

What is the relationship between intermolecular forces and boiling points?

Intermolecular forces play a crucial role in determining the boiling points of different substances. The stronger the intermolecular forces, the higher the boiling point of the substance. This is because stronger intermolecular forces require more energy to overcome, resulting in a higher boiling point.

Intermolecular Forces and Boiling Points:

There are several types of intermolecular forces that can exist between molecules, including:

• London Dispersion Forces: These are the weakest intermolecular forces and are caused by temporary fluctuations in electron distribution. Substances with only London dispersion forces tend to have low boiling points.
• Dipole-Dipole Forces: These forces occur between polar molecules with permanent dipoles. Substances with dipole-dipole forces have higher boiling points than those with only London dispersion forces.
• Hydrogen Bonding: This is a special type of dipole-dipole interaction that occurs when hydrogen is bonded to a highly electronegative atom like oxygen, nitrogen, or fluorine. Substances with hydrogen bonding have the highest boiling points.

Example:

For example, in the case of the given substances C3H8, CH3OH, and CH3OCH3, CH3OH has the highest boiling point because it can form hydrogen bonds. C3H8 has the lowest boiling point because it only has London dispersion forces, while CH3OCH3 falls in between as it also has London dispersion forces but no hydrogen bonding.