What type of change is sublimation?

Sublimation refers to the process where a solid transitions directly into a gas without passing through the liquid phase. This process is classified as an endothermic change because it requires the absorption of heat energy. In sublimation, the solid absorbs energy from its surroundings to overcome the intermolecular forces holding its particles in a fixed position, which enables them to escape as gas.

This energy absorption leads to a temperature increase in the surrounding environment, reflecting the endothermic nature of the process. Sublimation can be commonly observed with substances like dry ice (solid carbon dioxide) or ice in a very dry environment.

While sublimation is also a physical change—since it does not alter the chemical composition of the substance—it is essential to understand that the key characteristic that defines sublimation is its endothermic nature, requiring heat for the transition from solid to gas.