[english]

I know that this must have something to do with the length of the alkyl group attached to -OH.

Could someone tell me why?  I will give my assumption first, since I'm such a thinker 

C-H bonds are nonpolar, but I'm assuming that as C-H bonds become more numerous, electron induction has to occur over a longer molecular distance and thus the negative end of the dipole, in this case the -OH end, has a "harder time" attracting the electrons towards itself.

So CH2CH3OH must be more polar than CH3CH2CH2CH2CH2OH right?

[GSR]

hi,

you are partially correct.  -OH group is hydrophilic and alkyl group is lipophilic.when we consider the effect of alkyl group on solubility for lower members of the series the -OH group constitutes a large portion of the molecule, and these compounds are miscible with water. but, as the number of carbons increases, the solubility steadily decreases. a long chain with an -OH at one end of it is mostely hydrocarbon and its solubility is less.

the solubility of ethanol  ( in g/ 100g H2O) is infinity, whereas for 1-pentanol it is 2.3.

cheers
GSR