Which process describes a solid turning directly into a gas?

Which process describes a solid turning directly into a gas?

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

Answer: (A)

This item tests how phase changes can skip the liquid stage, turning a solid straight into a gas. Sublimation occurs when a solid gains enough energy to overcome the forces holding its particles, so they escape directly into the surrounding air as vapor. This often happens at higher temperatures or lower pressures for substances with a high vapor pressure in the solid state, such as dry ice, which sublimes at room temperature. The other processes involve a liquid forming or a gas becoming a solid: condensation is gas turning into liquid, melting is solid turning into liquid, and deposition is gas turning directly into a solid. So sublimation is the direct solid-to-gas change described.

This item tests how phase changes can skip the liquid stage, turning a solid straight into a gas. Sublimation occurs when a solid gains enough energy to overcome the forces holding its particles, so they escape directly into the surrounding air as vapor. This often happens at higher temperatures or lower pressures for substances with a high vapor pressure in the solid state, such as dry ice, which sublimes at room temperature. The other processes involve a liquid forming or a gas becoming a solid: condensation is gas turning into liquid, melting is solid turning into liquid, and deposition is gas turning directly into a solid. So sublimation is the direct solid-to-gas change described.