The process by which a solid turns into a gas is called sublimation. This phase transition occurs when the molecules in a solid gain enough energy to break free from their fixed positions and enter the gas phase without first becoming a liquid. Sublimation is commonly observed in substances like dry ice (solid carbon dioxide) and snow, which can "disappear" on warmer days. This process occurs under specific temperature and pressure conditions, typically at low pressure and higher temperatures for certain materials. Sublimation plays a significant role in various applications, including freeze-drying and the preservation of delicate items.