Heat energy supplied during the melting of a substance is utilised in :

1. increasing the kinetic energy of molecules
2. decreasing the potential energy of molecules
3. increasing the potential energy of molecules
4. decreasing the kinetic energy of molecules

increasing the potential energy of molecules

Reason — When a substance is melting, it transitions from a solid phase to a liquid phase. During this phase transition, the heat energy supplied is used to overcome the forces holding the molecules together in the solid phase. This process increases the potential energy of the molecules, allowing them to break free from their fixed positions in the crystal lattice. However, the kinetic energy of the molecules remains relatively constant during the phase transition, as the temperature remains constant until the phase change is complete. Therefore, the primary use of heat energy during melting is to increase the potential energy of the molecules