Which term describes the phase transition from solid to gas without passing through liquid?

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

Answer: (A)

Sublimation is a solid-to-gas transition without forming a liquid. It happens when a solid gains enough energy to overcome its intermolecular forces so that molecules escape directly into the vapor phase, often under low pressure or with substances that have a high vapor pressure. A common example is dry ice (solid carbon dioxide) at room temperature, which sublimates into CO2 gas. The reverse process is called deposition, where a gas becomes a solid. The other terms involve liquids: evaporation is liquid to gas, and condensation is gas to liquid, so they do not describe a direct solid-to-gas change.