Which phase change involves a solid changing directly into a gas?

Which phase change involves a solid changing directly into a gas?

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

Answer: (D)

Sublimation is the phase change where a solid gains enough energy that its particles go directly into the gas phase without forming a liquid first. This happens when the solid’s vapor pressure is significant at the given temperature (often under low pressure), so molecules escape into the air before the solid can melt. An example is dry ice turning into CO2 gas at room temperature. By contrast, melting is solid to liquid, evaporation is liquid to gas, and condensation is gas to liquid, none of which bypass the liquid stage. That direct solid-to-gas transition is what makes sublimation the correct choice.

Sublimation is the phase change where a solid gains enough energy that its particles go directly into the gas phase without forming a liquid first. This happens when the solid’s vapor pressure is significant at the given temperature (often under low pressure), so molecules escape into the air before the solid can melt. An example is dry ice turning into CO2 gas at room temperature. By contrast, melting is solid to liquid, evaporation is liquid to gas, and condensation is gas to liquid, none of which bypass the liquid stage. That direct solid-to-gas transition is what makes sublimation the correct choice.