Question

Give an example of a spontaneous process in which a system becomes less ordered and energy becomes less available to do work. What happens to the system’s entropy in this process?

Short answer

Evaporation is a spontaneous process in which a system becomes less ordered and unavailable to do work. The entropy of the system increases in this process.

Step-by-step solution

Give an example of a spontaneous process in which a system becomes less ordered.

Evaporation is the spontaneous process in which liquid is turned into vapor. In this process, the liquid molecules that receive enough energy will escape from the liquid phase into the vapor phase. So, the available energy to do work decreases. The particles are more closely arranged in a liquid compared to vapor, and they can’t move as freely as vapor molecules. So, liquids are more orderly than vapor. Therefore, the system becomes less ordered during evaporation as a transformation from liquid to vapor takes place.

Describe what happens to the entropy during this process.

Entropy is the measure of disorder or randomness. Particle motion will be more random in the vapor phase than in the liquid phase, and particles are more orderly in liquid form. So, during evaporation, entropy increases as the system become disordered.

Thus, during evaporation, the entropy of the system increases and it becomes less ordered, and the available energy to do work also decreases.