What contributes to the strength of intermolecular forces?

The strength of intermolecular forces is influenced significantly by the molecular mass of the compounds. Larger molecules generally have greater dispersion forces, which is a type of van der Waals force that arises from temporary dipoles due to electron movement. As molecular mass increases, so does the number of electrons present, which enhances the likelihood of these temporary dipoles forming. This results in stronger attractive forces between the molecules, leading to higher boiling points and melting points.

While boiling point can indicate the strength of intermolecular forces, it does not directly explain the contributing factor itself. Electronegativity of constituent atoms relates more to the type of bonds within the molecule rather than the intermolecular forces, and while packing efficiency can affect physical properties such as density, it does not assess the intrinsic strength of intermolecular interactions directly like molecular mass does. Therefore, molecular mass is the most direct contributor to the strength of those forces, making it the correct answer.