* 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 iron melts:

* State of matter changes: It transitions from a solid to a liquid.

* Chemical composition remains the same: Iron atoms are still iron atoms, just arranged differently.

Key Points:

* Melting and freezing are reversible physical changes.

* The chemical identity of the iron remains unchanged (it's still Fe).

* The process only involves changes in the arrangement of atoms, not the formation of new substances.