The term used for the reversible change of a substance from solid to gas is sublimation. This process occurs without passing through the liquid state and is typically observed in certain substances, such as dry ice (solid carbon dioxide) transitioning into carbon dioxide gas. Sublimation is an important phase change studied in chemistry and physical sciences, as it illustrates unique properties of certain materials and their interactions with heat and pressure. This reversible transformation is utilized in various applications, including freeze-drying and some manufacturing processes.