Which arrow in the following diagrams represents an endothermic phase transition?

Question

Quizplus · Accepted Answer

Endothermic phase transitions require an input of energy to occur, causing the surrounding temperature to decrease. In diagram I, the solid is melting into a liquid, which requires an input of energy. In diagram III, the liquid is evaporating into a gas, which also requires an input of energy. Therefore, choices II and IV are exothermic phase transitions, as they release energy and increase surrounding temperature.

Which Arrow in the Following Diagrams Represents an Endothermic Phase