water, H2O, and methane, CH4, have about the same mass and differ by only one type of atom. Why is the boiling point of water so much higher than that of methane?
Because the hydrogen bonding of water causes a relative high attraction among the molecules of water which implies that it is required more energy to separate them (the molecules in the gas phase are much more apart than in the liquid state).
The only force acting in the non-polar molecule of CH4 is the Van der Waals forces which are the weekest intermolecular forces.
