Final answer:
There is a direct relationship between higher molar mass and stronger dispersion forces because larger atoms and molecules have more electrons which contribute to temporary dipoles, resulting in stronger intermolecular attractions and higher melting and boiling points.
Step-by-step explanation:
Yes, there is a direct relationship between higher molar mass and stronger dispersion forces. Dispersion forces, also known as London dispersion forces or Van der Waals forces, are intermolecular attractions present in all substances with electrons. These forces result from the instantaneous position of electrons creating temporary dipoles in a molecule. As the molar mass of a substance increases, there are more electrons to contribute to these temporary dipoles, which means that larger and heavier atoms and molecules tend to have stronger dispersion forces than smaller and lighter ones.
This can be observed in the differences in physical states of the halogens at room temperature. The increasing molar mass from F2 (gas) to I2 (solid) is accompanied by strengthening of their dispersion forces, resulting in higher melting and boiling points. An increase in molar mass indicates a larger number of atoms and a greater extent of intermolecular attractions, necessitating more energy to overcome these forces during a phase change.
Furthermore, the concept of polarizability plays a significant role in understanding why higher molar mass correlates to stronger dispersion forces. Atoms with larger electron clouds are more polarizable, meaning their charge distributions are more easily distorted, leading to larger temporary dipoles and, in turn, stronger dispersion forces. This explains why larger molecules with higher molar masses typically have higher boiling and melting points, as compared to smaller molecules.