Why does boiling point depend on weight?

[phymatter]

1.Why does boiling point depend on weight ?
2.Does the vanderwall force depend on weight ?

 

[Ygggdrasil]

1. Because dispersion forces (a type of van der Waals force) depend on molecular size.

2. Dispersion forces (also known as induced dipole-induced dipole interactions) depend on the polarizability of the molecule (how easy it is to get an asymmetric distribution of electron in a molecule). As the number of electrons in a molecule and the size of the molecule increases, the polarizability increases.