International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What effect does weak intermolecular forces have on the boiling point of a substance, such as buckminsterfullerene?

1. Increases boiling point

2. Decreases boiling point

3. No effect on boiling point

4. Varies boiling point

The correct answer is: Decreases boiling point

Weak intermolecular forces, such as van der Waals forces, have a significant impact on the boiling point of a substance. In the case of buckminsterfullerene, which comprises spherical molecules held together by these weak forces, the strength of the intermolecular interactions is relatively low. As a result, less energy is required to overcome these forces when the substance is heated. This leads to a lower boiling point compared to substances with stronger intermolecular forces, where more energy would be necessary to break the interactions holding the molecules together. When weak forces are present, the molecules can easily move away from each other at lower temperatures, leading to a decrease in the boiling point. Therefore, substances like buckminsterfullerene exhibit a boiling point that corresponds to the weak nature of these forces, affirming the relationship between intermolecular strength and boiling point.