What do we call the transition where a solid changes directly into a gas without becoming liquid?

The process where a solid changes directly into a gas without first becoming a liquid is known as sublimation. This occurs under certain conditions, typically involving low pressure and/or high temperature, enabling the particles in the solid to gain enough energy to transition directly into the gaseous state. A common example of sublimation is dry ice (solid carbon dioxide), which sublimates at atmospheric pressure, turning directly into carbon dioxide gas without becoming liquid. Understanding this transition is important in various scientific applications, including freeze-drying and some industrial processes.

Other processes listed in the choices involve different states of matter: evaporation pertains to the transition from liquid to gas, while deposition refers to the direct transition from gas to solid, and condensation is the process of gas turning back into liquid. These processes highlight the different ways materials can change states under varying conditions.