Here's why:
* Melting is a phase change: During melting, the substance is transitioning from a solid to a liquid state. This change requires energy to break the bonds holding the molecules in a fixed, rigid structure.
* Energy goes into breaking bonds, not raising temperature: The energy being added to the substance isn't increasing the kinetic energy of the molecules (which would raise the temperature). Instead, it's being used to overcome the forces holding the molecules together in the solid state.
* Constant temperature plateau: As the substance melts, the temperature remains constant at the melting point until all the solid has transformed into a liquid. Then, the temperature can continue to rise if more heat is added.
Let me know if you'd like more details about the process of melting!
