* Physical Changes: Alter the form or appearance of a substance, but not its chemical composition.

Let's look at some examples:

Physical Change Equations:

* Melting Ice: H₂O(s) → H₂O(l) (Solid water changes to liquid water)

* Boiling Water: H₂O(l) → H₂O(g) (Liquid water changes to gaseous water)

* Dissolving Salt: NaCl(s) → Na⁺(aq) + Cl⁻(aq) (Solid salt dissolves into ions in water)

* Sublimation of Dry Ice: CO₂(s) → CO₂(g) (Solid carbon dioxide changes directly to gas)

Key Points:

* No new substances are formed. The chemical formula of the substance remains the same.

* Changes are usually reversible. You can often get the original substance back.

Let me know if you have a specific equation you'd like help with!