Why are methanol and ethanol liquids at room temp but methane and ethane are gases at room temp?

Question

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please help!

Answer 1

Because methanol and ethanol have hydrogen bonding, whereas methane and ethane only have london dispersion forces (which are much weaker).

Answer 2

Methanol and ethanol are both alcohols which contain the OH bond.

Like water, the O-H group causes there to be strong forces of attraction between OH groups known as Hydrogen bonding.

Methane and ethane only contain C-C and C-H bonds but no O-H bonds and there cannot be H bonding between Hs and/or Carbon atoms. The forces of attraction between methane and ethane molecules are much weaker than those in methanol and ethanol.

The forces of attraction are the forces which make a certain compound a solid, liquid, or gas at room temperature.  

Answer 3

The alcohols methanol and ethanol have much higher boiling points than the corresponding alkanes because of hydrogen bonding. To boil a substance like an alcohol you have to break all of those hydrogen bonds and that takes quite a bit of energy. Water has a high BP for the same reason.

For a brief discussion of hydrogen bonding see

en.wikipedia.org/wiki/Hydrogen_bond