What causes the high melting and boiling points of alcohols?

The high melting and boiling points of alcohols can be attributed primarily to hydrogen bonding, which is a strong type of intermolecular force. In alcohols, the presence of the hydroxyl (-OH) group allows for the formation of hydrogen bonds between the molecules. This occurs because the hydrogen atom attached to the oxygen is highly polar, leading to a significant attraction between the positively charged hydrogen of one alcohol molecule and the negatively charged oxygen of another.

These hydrogen bonds require a considerable amount of energy to break, thus raising the melting and boiling points of alcohols in comparison to those of substances that only exhibit weaker intermolecular forces, such as Van der Waals forces. Although other interactions, like induced dipole-dipole interactions, play a role in some contexts, they are not the primary factor in the context of alcohols' melting and boiling points.

Regarding the other options, while ionic bonds are strong, they are not present in alcohols. The term "non-polar chains" does not apply to alcohols that contain polar functional groups. Lastly, while molecular weight can influence boiling and melting points, the strong hydrogen bonding has a more pronounced effect in this case.