Elemental iodine can be heated to show sublimation, where it changes directly from a solid to a purple vapor and then recrystallizes on a cooled surface without passing through a liquid phase.

1. Place about 2 g of iodine crystals into a 500 ml Erlenmeyer flask.
2. Cover the mouth of the flask with a watch glass that has ice placed on top.
3. Slowly heat the flask on a hot plate.
4. Observe as purple iodine vapor forms and deposits solid iodine crystals on the underside of the watch glass.

Chemistry experiment 47 - Sublimation of Iodine - koen2all:

📄 The Sublimation of Iodine - lsa.umich: https://lsa.umich.edu/content/dam/chem-assets/chem-docs/teaching%20lab%20docs/Sublimation%20of%20Iodine.pdf

• Use a test tube instead of a flask for a smaller-scale demonstration.
• Capture time-lapse images to show the sublimation and deposition process.
• Compare sublimation with substances that melt before vaporizing, highlighting differences in phase changes.

• Wear safety goggles, gloves, and a lab coat.
• Iodine vapors are toxic and irritating; perform the demonstration in a fume hood.
• Avoid skin contact with iodine crystals.
• Dispose of iodine-containing waste according to hazardous chemical waste guidelines.

• What type of phase change does iodine undergo in this experiment? (Sublimation, solid to gas.)
• Why do iodine crystals form on the cooled watch glass? (The vapor condenses and deposits as solid iodine upon cooling.)
• How does sublimation differ from melting and boiling? (Sublimation skips the liquid phase, going directly from solid to gas.)
• Can you name other substances that undergo sublimation under standard conditions? (Dry ice, naphthalene.)