AAMC FL Practice Exam

What process involves a solid changing directly to a gas?

1. Condensation

2. Evaporation

3. Sublimation

4. Deposition

The correct answer is: Sublimation

Sublimation is the process where a solid transitions directly into a gas without first becoming a liquid. This change occurs when the particles of a solid gain enough energy, typically through heating or a decrease in pressure, to overcome the forces holding them together in a solid state. As a result, the solid molecules escape directly into the gaseous phase. This phenomenon can be observed with substances like dry ice (solid carbon dioxide), which sublimates at temperatures and pressures typical of Earth's atmosphere, rapidly turning into carbon dioxide gas. Understanding sublimation is crucial in various applications, including freeze-drying processes and the behavior of certain materials in different environmental conditions. Other processes like evaporation involve a liquid becoming a gas, while condensation and deposition are processes where gas changes into a liquid or solid, respectively.