Which property increases as the molecular size of alcohols increases?

As the molecular size of alcohols increases, the melting and boiling points rise due to the increasing strength of intermolecular forces. Alcohols contain hydroxyl (-OH) groups, which can engage in hydrogen bonding. As the size of the alcohol molecule increases, there are more carbon and hydrogen atoms in the molecule, leading to an increase in the number of van der Waals (dispersion) forces as well.

These enhanced intermolecular forces require more energy to overcome, which translates into higher melting and boiling points. For example, as you compare smaller alcohols like methanol to larger ones like octanol, you’ll observe that the boiling point rises significantly with increasing molecular size.

In contrast, water solubility tends to decrease as the molecule becomes larger, primarily due to the increasing hydrophobic character of longer hydrocarbon chains. Flammability may not consistently increase with size either, as larger alcohols may burn less readily than their smaller counterparts. Reactivity with acids does not show a direct dependence on molecular size in the same way that boiling and melting points do.