I would recommend drawing both molecules to identify the key functional groups and relative sizes of the two molecules before attempting to write an answer. Answer: Ethanol molecules have hydrogen bonding interactions between them, ethene molecules don't. (1) Ethene molecules only have van der waals interactions between them, which are weaker than hydrogen bonds. (1) More energy is required to break the stronger hydrogen bonds between ethanol molecules than the weaker van der waals forces between ethene molecules. (1)