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Narrative
Iodine crystals are poured into a large cylinder. Like most alkenes, cyclohexene reacts only sluggishly with iodine. But when a-pinene is poured into iodine, the exothermic reaction vaporizes iodine. The extra energy comes from relief of ring strain in the a-pinene molecules.

Discussion
Mixing solid iodine and cyclohexene shows little reaction but mixing iodine and a-pinene produces a very vigorous exothermic reaction and sublimation of solid iodine to dense iodine vapor.

There are several common pronunciations of the word 'iodine'. Variations of this movie and the "Historical Note" movie are provided with variations in pronunciation via these links:
Addition of Iodine to a-Pinene
Historical Note