What is the process of a solid turning directly into a gas called?

The process of a solid turning directly into a gas is known as sublimation. This occurs when the molecules of the solid gain enough energy to overcome the forces holding them in a solid state, allowing them to transition directly into the gaseous phase without first becoming a liquid. An everyday example of sublimation is dry ice (solid carbon dioxide), which slowly converts into carbon dioxide gas at room temperature without turning into a liquid first.

In contrast, condensation refers to the process of a gas turning into a liquid, which is the opposite of sublimation. Evaporation is the process by which a liquid transitions into a gas, and freezing is the conversion of a liquid into a solid. Therefore, sublimation uniquely describes the transition directly from solid to gas, making it the correct answer.