The most eye-catching thing about iodine sublimation is the bright purple color of the vapor. But the halogen’s crystalline solid form has its own, often overlooked, beauty too, says Brent Rubio, an associate professor of Chemistry at the University of Hawai’i. In this lesson, Rubio’s general chemistry lab students sublime solid iodine to a gas and then redeposit it as a solid to learn about physical versus chemical changes. Chemists use sublimation as a purification method for chemicals like iodine because nonvolatile impurities are left behind when the compound vaporizes and then resolidifies on a cold, clean surface. Rubio snapped this photo with his phone camera of his students’ freshly deposited crystals under a microscope at 40× zoom.
Submitted by Brent Rubio
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