How does molecular weight affect boiling point?

Molecular weight significantly impacts the boiling point of a substance due to the relationship between molecular mass and intermolecular forces. As molecular weight increases, the boiling point typically increases as well. This correlation arises because larger molecules tend to have greater surface areas and more electrons, leading to stronger London dispersion forces, which are a type of van der Waals force.

These intermolecular attractions require more energy (in the form of heat) to overcome, resulting in a higher boiling point. For example, larger hydrocarbons exhibit progressively higher boiling points compared to their smaller counterparts due to these enhanced intermolecular interactions.

In contrast, smaller molecules usually have weaker intermolecular forces, which means that less energy is needed to transition them from the liquid phase to the gas phase, resulting in lower boiling points. Thus, an increase in molecular weight generally correlates with an increase in boiling point, making the statement that a larger molecular weight leads to a higher boiling point accurate in most cases.