Question

why ethanol dissolves in water, but ethane does not?

Answer 1

Ethanol is that type of compounds which have some polarity in it while ethane is overall non-polar so due to this polarity, ethanol is soluble in water due to hydrogen bonding while ethane not.

Ethanol is an alcohol, which is a a polar molecule. the -OH functional group of Ethanol has the O- and H+ terminals, thus it is soluble in liquid water.

Where as Ethane,which is an Alkane, is not a polar molecule as it doesn't have any opposite charged terminals,so it doesn't solute in water.

Answer 2

Like dissolves like
ethanol is polar, dissolves in water because water is polar
ethane is covalent and not like water
for more reading http://www.funqa.com/chemistry/987-Chemistry.html