Some solid substances when heated get converted directly to the gaseous or vapour state without first passing through the liquid state. When this vapour or gas is cooled, it gets converted directly into a solid, without passing through the liquid state. Such change of state of a solid directly into gas or vapour and back to the solid state, without passing through the liquid state, is called as sublimation. When a sublimable solid substance is heated, it is said to 'sublime' into a gaseous state; and when sublimable substances are cooled from their vapour state, the solid obtained is called the 'sublimate'. Some sublimable substances are: iodine, camphor, naphthalene, dry ice carbon dioxide) etc.