Skipping liquids: Sublimation

  Most substances go through the logical progression from solid to liquid to gas as they’re heated (or vice versa as they’re cooled). But a few substances go directly from the solid to the gaseous state without ever becoming a liquid.   Scientists call this process sublimation. Dry ice — solid carbon dioxide, written as CO₂(s) — is the classic example of sublimation. You can see dry ice pieces becoming smaller as the solid begins to turn into a gas, but no liquid forms during this phase change.  The process of sublimation of dry ice is represented as

Besides dry ice, mothballs and certain solid air fresheners also go through the process of sublimation. The reverse of sublimation is deposition — going directly from a gaseous state to a solid state.