Final answer:
Sugar has a low melting point due to the weak dispersion forces between its relatively small, nonpolar molecules.
Step-by-step explanation:
Sugar (sucrose) has a low melting point due to the nature of its intermolecular forces. Sugar is categorized as a molecular crystal and consists of neutral molecules. The attractive forces between these molecules are relatively weak, consisting mainly of dispersion forces. These forces are the result of temporary dipoles formed in the electron cloud, due to the constant motion of electrons. The strength of these dispersion forces is influenced by the molecular size and polarizability of the molecules. In the case of sugar, the relatively small size of the sucrose molecule and its nonpolar nature contribute to weak dispersion forces and a low melting point.