Question

Whenever a body changes from solid to liquid, the change is
A) Endothermic
B) Exothermic
C) Neutral
D) Isobaric

Answer 1

Whenever a substance changes its state from solid to liquid, its entropy increases. To gain this entropy, it needs some energy. Endothermic is the absorption of energy. Exothermic is the release of energy. In neutral conditions, no change in energy occurs. In isobaric condition, the pressure is constant.

Complete step by step solution:
A) Endothermic
Endothermic reaction or change is that kind of reaction or change which requires extra outside energy to occur. The outside energy can be in any form. Mostly heating is done to change the state of matter. Here, the system takes energy from the surroundings. Common examples of it are melting of ice, evaporation of water to vapour, melting of wax etc.

B) Exothermic
Exothermic reaction or change is that kind of reaction or change which releases energy to occur. Energy can be in any form. Mostly it gets released in the form of heat. It is done to change the state of matter. Here, the system gives out energy to the surroundings. Common examples of it are formation of ice, condensation of water to vapour, solidification of wax etc.

C) Neutral
Neutral is referred to as no change. Here, no transfer of energy occurs between the system and the surroundings.

D) Isobaric
It refers to any change where the pressure is kept constant.
Whenever solid changes to liquid, its entropy increases as the particles in liquid are freer to move then that of solid. To increase this entropy, some amount of energy is needed. This can be given in any form from outside. Thus we can say it’s a type of endothermic change.

So, option (A) is the answer.

Note: Whenever any substance changes its state, entropy change occurs. When the state change is into a tough or rigid form, entropy decreases, and hence the change is exothermic. But when the state change is into a softer form or flowy form, entropy increases, and hence the change is endothermic