Chemistry of Solids
12.1 Phase Change and Solids
Subjects: Properties of solids, Phase change
Description: The sublimation of iodine is demonstrated.
- 250 mL Erlenmeyer flask with stopper
- Hot plate*
- Heat gun (optional)*
‡Iodine is located in the chemical storage cabinets.
*Shared item: The hot plates are located in the top drawer in the central bench opposite the chemical storage cabinets. The heat gun is in the drawer below.
- Place the flask on the hot plate. Turn the hot plate on to low temperature.
- Warm the flask.
- Iodine will sublimate to iodine vapors.
- Let the flask cool to room temperature. The iodine vapors will crystallize.
Alternatively you can heat the flask with the heat gun.
Sublimation is the process of the conversion of a solid directly to a gas. Sublimation is an endothermic process, absorbing energy like evaporation or melting. This energy is called the enthalpy of sublimation:
∆sublimationH = energy required as heat
Unlike CO2, which sublimes at room temperature, iodine requires more energy in the form of heat to transform from a solid to a vapor.
Avoid inhaling iodine vapors and take precautions not to drop the flask with iodine.
The flask with iodine can be saved and reused.
1. J. Kotz, P. Treichel, J. Townsend; Chemistry & Chemical Reactivity; 7th Ed, Teachers Edition; Brooks/Cole; 2009; p. 606