In this lesson, students learned about the separation of solid-solid mixtures using sublimation, a process where a solid transitions directly into a gas when heated without forming a liquid. The instructor demonstrated how to separate a mixture of iodine and sand using a setup that captures the sublimed gas on a cold surface, allowing the iodine to solidify while leaving the non-volatile sand behind. Other examples of substances that can be separated by sublimation include carbon dioxide, hydrous iron chloride, aluminum chloride, and ammonium chloride.