$(a)$ Enumerate the changes that take place inside the matter during the change of states.
$(b)$ When a solid melts,its temperature remains the same. Give reason.

(N/A) During a change of state,the heat energy supplied increases the kinetic energy $(KE)$ of the particles,which helps them overcome the intermolecular forces of attraction. This leads to a change in the arrangement of particles,causing the matter to transition from one state to another (e.g.,solid to liquid).
$(b)$ When a solid melts,the temperature remains constant because the heat energy supplied is entirely consumed as latent heat of fusion. This energy is used to overcome the strong intermolecular forces of attraction holding the solid particles together,rather than increasing the kinetic energy of the particles.