What is the phase change from a solid to a gas called?

The phase change from a solid to a gas is termed sublimation. This process occurs when a substance transitions directly from the solid state to the gaseous state without passing through the liquid phase. A common example of sublimation is dry ice (solid carbon dioxide), which slowly turns into gas at room temperature.

In contrast, condensation is the process where a gas changes into a liquid, which is the reverse of sublimation. Melting refers to the change from solid to liquid, while evaporation describes the transition from liquid to gas. These processes clearly illustrate the various changes in states of matter, but sublimation specifically captures the unique direct transition from solid to gas.