* NaCl is table salt (sodium chloride).

* H2O is water.

* When you mix salt and water, you are creating a saltwater solution. The salt dissolves in the water, but its chemical composition remains the same.

* The salt molecules (NaCl) are surrounded by water molecules (H2O), but the bonds within the salt molecule itself don't break.

* You can easily separate the salt from the water by evaporating the water, leaving the salt behind.

Key characteristics of physical changes:

* No new substances are formed.

* Changes are usually reversible.

* Changes involve a change in form or appearance, but not in chemical composition.

Let me know if you'd like more examples of physical and chemical changes!