* Physical Changes: Alter the form or appearance of a substance but not its chemical composition.

* Chemical Changes: Result in the formation of new substances with different chemical properties.

When solid iodine sublimes, it changes directly from a solid to a gas (skipping the liquid phase). The iodine molecules themselves remain the same (I₂), only their state of matter changes. There's no new chemical substance formed.

Key points:

* The purple vapor is still iodine (I₂).

* The change is reversible; the vapor can condense back into solid iodine.

* No new chemical bonds are formed or broken.

Therefore, sublimation of iodine is a physical change.