Enhanced heat capacities of molten salts and oxide nanoparticle mixtures (nanomaterials) have been recently reported. These molten salts are used as thermal energy storage in solar thermal power, and the enhancement of their heat capacities are expected to significantly decrease the cost of electricity. However, the mechanism for the enhanced heat capacity of these nanomaterials is unknown. Different phase transition of molten salts near nanoparticles has been recently proposed to be primarily responsible for the enhanced heat capacity of this type of nanomaterials. Hence, we present an experimental validation of the proposed mechanism for the enhanced heat capacity of nanomaterials.