Answer: Option (b) is the correct answer.
Explanation:
In a solid, molecules are closely held together by strong inter molecular forces of attraction. As a result, the molecules are not able to move freely in a solid state.
So, when a solid absorbs heat or is heated at high temperature then intermolecular forces between the molecules break. As a result, molecules start to move randomly and thus they gain kinetic energy.
For example, ice cube melts at room temperature because it absorbs heat from the surrounding.
Also, it is known that in an endothermic reaction heat is absorbed by reactants in a chemical reaction whereas in a exothermic reaction heat is released in a chemical reaction.
Thus, we can conclude that endothermic reaction takes place when the melting of a solid occurs.
