Question

Why does boiling point depend on mass?

Answer 1

The intermolecular forces which is present in all molecules is London dispersion forces.

Strength of this force depends on the polarizability that is the ease with which their electron clouds can be distorted.

Strength increases with # of electrons in the molecule.

Molecule with higher molecular mass contains more electrons, and the energy required to overcome this forces in order to convert a liquid to a gas will be higher.
Hence we can say that boilingpoint depends on the mass of the substance. for example Helium boiling point is -269*C Argon boiling point is -186*C.

The smaller the atom, the harder it is to distort the e- cloud (low polarizability) since the electrons are closer tothe nucleus

The larger the atom, the easier it is to distort the e- cloud (high polarizability) because the valent electrons are further away from the nucleus and experience shielding from the nucleus’ pull.

The second reason is Surface Area --- increasing surface area, increasing boiling point