* Physical Changes: Alter the form or appearance of a substance but don't change its chemical composition.

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

When something becomes powdery, its physical form is altered. For example, a solid chunk of sugar becomes a powder when crushed. The chemical makeup of the sugar (sucrose) remains the same, it's just in a different physical state.

Let me know if you have any more questions!