Sublimation of Iodine

Below a substance's triple point, heating can cause the solid to sublime directly to the gas phase. Many students come to lessons on particle theory and/or changes of state with some prior experience of sublimation (often that of dry ice) and a demonstration to show it in action can be valuable.

Schools should have access to dry ice either by production on site or through contacts with local university departments or industry. Sometimes, however, it can be impractical to use dry ice.

Iodine is commonly found in schools, sublimes at accessible temperatures and has the advantage of being able to easily display the reverse phase transition: deposition.