What is the process called when a solid changes directly to a gas?

The process when a solid changes directly to a gas is known as sublimation. This occurs without the substance first becoming a liquid. A classic example of sublimation is the transition of dry ice (solid carbon dioxide) directly into carbon dioxide gas at room temperature. Sublimation involves the absorption of heat, which allows the solid molecules to gain enough energy to overcome intermolecular forces and disperse into the gas phase.

In contrast, vaporization refers to the transition from liquid to gas, which can occur through evaporation or boiling, while melting is the process where a solid becomes a liquid. Evaporation is a type of vaporization that occurs at the surface of a liquid when it is not boiling. Understanding these distinct processes is crucial in the study of states of matter and phase transitions.