Sublimation is the process by which which occurs?

• A. The process of turning a liquid into a gas
• B. The process by which a solid changes directly into a gas
• C. The process of changing a gas into a liquid
• D. The process of turning a solid into a liquid

Answer: (B)

Sublimation is the direct change of a solid into a gas. In this process, the particles in a solid gain enough energy to overcome the forces holding them in a lattice and jump straight into the gas phase, bypassing the liquid stage. This often happens under low pressure or when the solid has a relatively high vapor pressure for that temperature, such as dry ice at room temperature turning into carbon dioxide gas. This is different from melting, which is solid to liquid, and from evaporation or boiling, which are liquid to gas. It’s also different from condensation, which is gas to liquid. Sublimation is typically endothermic, meaning it absorbs heat as the solid transforms directly into vapor.