Question

Is the molecular masses of hydrocarbons increase their boiling point and melting increase or decrease?

Answer 1

With increase in molar mass, the melting point and boiling points of hydrocarbons increases generally.

It is because, with increase in molar mass, the molecule becomes larger and so the van der waal's forces and other binding forces between those molecules become stronger, which holds the particles very firmly together in solid or liquid phase and so it requires more energy to break these bonds and thus the melting and boiling points of the hydrocarbons increases.