A solid begins to melt when?

A.

constituent particles acquires a greater kinetic energy

B.

energy of vibration of particles of the solid is less than the intermolecular forces

C.

constituent particles acquires energy above the average kinetic energy

D.

energy of vibration of particles of the solid equals the intermolecular forces

Correct answer is D

When a solid is heated, the particles are given more energy and start to vibrate faster. At a certain temperature, the particles vibrate so much that their ordered structure breaks down. At this point the solid melts into liquid.