Exothermic processes are those that release heat to the surroundings. In the context of phase changes, we need to identify which of the given options involves a release of energy.
Among the options:
- a. melting and boiling – Both processes require heat to occur, meaning they are endothermic.
- b. freezing and sublimation – Freezing is exothermic because it releases heat, but sublimation is endothermic.
- c. melting and condensation – Melting is endothermic, while condensation is exothermic as it releases heat.
- d. condensation and freezing – Both of these processes are exothermic. Condensation releases heat as gas turns into liquid, and freezing releases heat as liquid turns into solid.
Based on this analysis, the correct answer is d. condensation and freezing, as both processes involve the release of energy.