* 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 is warmed, it undergoes sublimation. This means it changes directly from a solid to a gas, skipping the liquid phase. The purple vapor is still iodine (I₂), just in a gaseous state. The chemical composition hasn't changed, only the physical state.

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