What does sublimation refer to in terms of phase transition?

Sublimation is a specific phase transition that occurs when a substance moves directly from a solid state to a gas state without first becoming a liquid. This process usually requires the input of energy in the form of heat, which provides the necessary energy for the solid molecules to overcome the intermolecular forces that hold them in a rigid structure.

Common examples of sublimation include dry ice (solid carbon dioxide) transitioning to carbon dioxide gas at atmospheric conditions and the phenomenon of snowflakes gradually shrinking without melting into water. Understanding sublimation is important in various applications, including freeze-drying and the behavior of certain materials in different environmental conditions. Recognizing that sublimation bypasses the liquid phase helps distinguish it from other phase transitions, such as melting or evaporation, which involve passing through a liquid state.