Which phase change is described as solid turning directly into gas?

Which phase change is described as solid turning directly into gas?

• A. Condensation
• B. Evaporation
• C. Deposition
• D. Sublimation

Answer: (D)

A solid turning directly into a gas is sublimation. In sublimation, particles in a solid gain enough energy to overcome intermolecular forces and enter the gas phase without first becoming a liquid. This can happen under conditions of low pressure or when the solid has a high vapor pressure at a given temperature—think of dry ice (solid carbon dioxide) that disappears right into CO2 gas at room temperature, or certain solids like iodine that sublimate under heat. In contrast, condensation is gas turning into liquid, and evaporation is liquid turning into gas at the surface. Deposition is gas turning directly into solid. So the described process fits sublimation because it skips the liquid stage entirely.

A solid turning directly into a gas is sublimation. In sublimation, particles in a solid gain enough energy to overcome intermolecular forces and enter the gas phase without first becoming a liquid. This can happen under conditions of low pressure or when the solid has a high vapor pressure at a given temperature—think of dry ice (solid carbon dioxide) that disappears right into CO2 gas at room temperature, or certain solids like iodine that sublimate under heat.

In contrast, condensation is gas turning into liquid, and evaporation is liquid turning into gas at the surface. Deposition is gas turning directly into solid. So the described process fits sublimation because it skips the liquid stage entirely.