Final answer:
The melting point is lower after hydrolysis because it transforms compounds with stronger bonds into smaller molecules with weaker intermolecular forces, reducing the melting point.
Step-by-step explanation:
The melting point is generally lower after hydrolysis because the process involves breaking larger molecules into smaller ones. Upon hydrolysis, the original compound, which may have had ionic or strong covalent bonds, is broken down into components with weaker intermolecular forces. The lower melting point is due to a reduction in the bonding strength that occurs when large polymers or aggregates are split into smaller molecules.
For example, during hydrolysis, a disaccharide like maltose is broken into two glucose monomers, which have weaker intermolecular forces compared to the original disaccharide. The enthalpy of fusion and melting point of a solid depend on the strength of attractive forces present in the crystal. Since the hydrolysis products have weaker forces holding them together, the melting point after hydrolysis is lower.
Similarly, when nonvolatile solutes such as glucose are dissolved in water and disrupt the equilibrium at the freezing point, the added particles interfere with the crystalline structure formation, effectively lowering the melting point of the solution. This is comparable to the impact of impurities in bulk materials, where the presence of impurities typically leads to a reduction in melting temperatures.