Question

Why does water (H2O) have a significantly higher boiling point than methane (CH4)? Hydrogen forms a stronger covalent bond with oxygen than with carbon. Hydrogen forms a weaker covalent bond with oxygen than with carbon. Water molecules are attracted to one another by hydrogen bonds. Water molecules are made of fewer atoms than methane molecules.

Answer 1

The attraction of inter-molecular forces between molecules is defined by a general term "Van der Waals forces". It is the weak interactions caused by momentary changes in electron density in a molecule.

Inter-molecular forces that are present between hydrogen atom which is bonded to highly electronegative atom ($F, O, and N$) and the lone pair electrons present in the other molecule on these electronegative atoms is known as hydrogen bonding.

The type of interactions between methane, $CH_4$ is Van der Waals interactions whereas in water, $H_2O$ is hydrogen bonding.

Since, the hydrogen bond is stronger than the Van der Waals forces so, it results in higher strength between the molecule possessing hydrogen bonding. Thus, molecules possessing hydrogen bonds will have higher boiling point than the molecules which possess Van der Waals forces.

Hence, water ($H_2O$) have a significantly higher boiling point than methane ( $CH_4$ ) because water molecules are attracted to one another by hydrogen bonds.