1.Butanoic acid has stronger intermolecular forces (hydrogen bonding) because it has two highly electronegative oxygen atoms in its structure, whereas butan-1-ol has only one. Therefore the acid molecules can form stronger bonds between neighbouring molecules. 2.Whilst carboxylic acids can form hydrogen bonds with neighbouring water molecules, owing to the presence of the two oxygen atoms present on the carboxyl group, as the chain length increases the hydrophobic nature of the molecule becomes more defined- it is more difficult for water molecules to surround and dissolve these larger molecules, as the non functional carbon chain has no oxygen atoms to which it can from hydrogen bonds with water.