Final answer:
Kinetic energy remains constant during phase changes, as energy is absorbed or released as potential energy. Endothermic processes absorb energy, while exothermic processes release energy.
Step-by-step explanation:
Phase changes are closely related to changes in kinetic energy and potential energy of the molecules within a substance. During a phase change, the temperature of a substance remains constant, which means kinetic energy does not increase; instead, energy is either absorbed or released in the form of potential energy. Therefore, the correct answer is c. Kinetic energy remains constant during phase changes. When a substance undergoes a phase change from a more ordered state to a less ordered state (for example, from solid to liquid or liquid to gas), energy is absorbed to overcome intermolecular forces and increase the potential energy of the molecules. This process is endothermic. Conversely, when changing from a less ordered state to a more ordered state (for example, from gas to liquid or liquid to solid), energy is released, decreasing the potential energy of the molecules, and this process is exothermic.