Question 17

Sublimation is the process when snow changes directly to a gas in a very cold region.

Sublimation refers to the transition of a substance from a solid state directly to a gas without passing through the liquid state. In very cold regions, snow can undergo this process when the temperature and pressure conditions allow for direct conversion to vapor.

A) evaporation

Evaporation is the process by which liquid turns into vapor, typically occurring at temperatures below the boiling point. Since the question specifically refers to snow, which is solid, evaporation does not apply in this context and is therefore incorrect.

B) condensation

Condensation is the process where gas transforms into a liquid. This is the opposite of what occurs when snow changes directly to a gas, making this option incorrect for the question being asked.

C) sublimation

Sublimation is indeed the process that describes the direct transition of snow (solid) to gas. This phenomenon occurs under specific conditions, which can be present in very cold regions, making this option the correct choice.

D) decomposition

Decomposition refers to the breakdown of a substance into simpler components, typically involving a chemical change. This is unrelated to the physical phase change from solid to gas, thus rendering this option incorrect as well.

Conclusion

Sublimation is the only process listed that accurately describes the direct change from solid snow to gas without passing through a liquid phase. All other options either describe processes that do not apply to solids transitioning to gas or are fundamentally unrelated to the question's context.