All atoms and molecules can develop temporary uneven electron distributions. Polarizability can make dispersion substantial. Hydrogen bonding requires H bonded to N, O or F interacting with an available lone pair; boiling separates molecules rather than breaking all covalent bonds.

The model has a domain of validity. Explain its assumptions before using it in a changed context, then compare your prediction with evidence.

• Intermolecular forces act between molecules. Dispersion arises from fluctuating charge; hydrogen bonding is a stronger specific attraction in suitable molecules.
• Do not call every bond containing hydrogen a hydrogen bond. Dispersion is not always negligible.