* 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.

Sublimation of naphthalene involves a change in state from solid to gas, but the chemical makeup of the naphthalene molecules remains the same. It's simply a change in how the molecules are arranged and moving.

Think of it like this: If you were to freeze water (H2O), it would become ice, a solid. Melting the ice back into liquid water is a physical change because you're still dealing with H2O molecules, just in different states of matter. Sublimation is similar, just a direct transition between solid and gas.