* Physical Change: A physical change alters the form or appearance of a substance but doesn't change its chemical composition.

* Melting is a classic example. Ice (solid water) melts into liquid water. The chemical formula (H₂O) remains the same; only the arrangement of the molecules changes.

* Chemical Change: A chemical change results in the formation of new substances with different chemical compositions.

* Examples include burning wood (forming ash and gases), rusting iron (forming iron oxide), or baking a cake (forming new molecules through chemical reactions).

Key indicators of a chemical change:

* Production of a gas: Bubbles, fizzing, or a change in odor.

* Formation of a precipitate: A solid forming from a solution.

* Color change: A change in hue that isn't simply due to light reflection.

* Heat or light production/absorption: A change in temperature or the emission of light.

In summary: Melting is a physical change because it only changes the state of matter, not the chemical composition of the substance.