Final answer:
An endothermic process absorbs heat, and among the choices provided, C (mixing of barium hydroxide with ammonium chloride leading to ice formation) correctly describes an endothermic reaction.
Step-by-step explanation:
The question asks which of the given options describes an endothermic process. An endothermic process is one that absorbs heat from its surroundings. Upon review of the choices, option C, which describes the mixture of barium hydroxide with ammonium chloride forming ice crystals on the outside of the container, is an endothermic reaction. Ice forming indicates that heat is absorbed from the environment, causing the container to feel cold.
Labeling endothermic and exothermic processes:
- Water boiling is endothermic because heat must be added to the water to make it boil.
- Gasoline burning is exothermic as it releases heat.
- Ice forming on a pond is exothermic because heat is removed from the water as it freezes.