What is the term for a solid changing directly into a gas without becoming a liquid? The process is called sublimation.
During sublimation, particles leave a solid’s surface and enter the gas phase without passing through a liquid state. The process absorbs energy, because particles must overcome the attractive forces holding them in the solid structure.
Dry ice is the best-known example: at ordinary atmospheric pressure, solid carbon dioxide changes directly into gas at about −78.5 °C. Ice can also sublime slowly in cold, dry conditions, which helps explain why snow disappears without visibly melting. Freeze-drying uses reduced pressure to remove water from frozen foods and medicines by sublimation.
The reverse process is deposition, in which a gas becomes a solid directly; frost is a familiar example. Evaporation is different because it describes liquid changing into gas, while condensation describes gas changing into liquid.