For iodine crystals to sublime on heating, the molecules must acquire energy that is?
Answer Details
For iodine crystals to sublime on heating, the molecules must acquire energy that is greater than the forces of attraction in both the solid and liquid phases. Sublimation is the process by which a solid directly turns into a gas without passing through the liquid phase. This requires a significant amount of energy, as the molecules in the solid phase are held together by strong intermolecular forces of attraction.
When iodine crystals are heated, the energy from the heat causes the iodine molecules to vibrate faster and increases the distance between them. At a certain temperature, the energy of the iodine molecules becomes great enough to overcome the intermolecular forces holding them together in the solid phase. The molecules break free from the solid and form a gas, bypassing the liquid phase altogether.
Therefore, the energy required to sublime iodine is greater than the forces of attraction in both the solid and liquid phases. If the energy is less than the forces of attraction in the solid or equal to the forces of attraction in the solid, the iodine crystals will not sublime but instead remain in the solid phase. If the energy is only enough to melt the solid, the iodine will only melt and not sublime.