Hydrogen bonds are considerably stronger than van der Waals forces.

Both hydrogen bonds and van der Waals forces are types of intermolecular forces, which refer to the interactions that occur between molecules. However, these two categories of forces differ significantly in strength. Hydrogen bonds are recognized as the strongest form of intermolecular forces, while van der Waals forces are the weakest.

Hydrogen bonding occurs when a hydrogen atom is covalently bonded to a highly electronegative atom, such as nitrogen, oxygen, or fluorine. The hydrogen atom is then attracted to another electronegative atom in a separate molecule. This interaction results in a strong dipole-dipole attraction, which is substantially more robust than the temporary dipoles responsible for van der Waals forces. In fact, the strength of a hydrogen bond can be up to $30$ times greater than that of a van der Waals force.

Conversely, van der Waals forces are weak attractions that exist between all atoms and molecules. These forces arise from temporary fluctuations in electron distribution around an atom or molecule, which create a transient dipole. This temporary dipole can induce a dipole in a neighboring atom or molecule, resulting in a weak attractive force known as a van der Waals force. The inherently transient nature of these interactions, which depend on the proximity of the atoms or molecules, makes them much weaker than hydrogen bonds.

The differences in strength between these intermolecular forces have significant implications for the physical properties of substances. Because hydrogen bonds are stronger, substances capable of forming them typically exhibit higher boiling points, melting points, and viscosities compared to similar substances that can only form van der Waals forces. This is due to the greater amount of energy required to disrupt the stronger hydrogen bonds during phase transitions.

In conclusion, while both hydrogen bonds and van der Waals forces play crucial roles as intermolecular forces, hydrogen bonds are notably stronger due to their dipole-dipole characteristics and the high electronegativity of the involved atoms. This strength leads to distinct physical properties in substances that engage in hydrogen bonding, setting them apart from those that rely solely on van der Waals forces.