* No new substances are formed: The sugar simply dissolves in the vinegar. The sugar molecules are still sugar molecules, and the vinegar molecules are still vinegar molecules.

* The change is reversible: You can easily separate the sugar from the vinegar by evaporation. The sugar will be left behind, and you can recover the vinegar.

Key characteristics of physical changes:

* Changes in state (like dissolving)

* Changes in appearance

* No new substances are formed

* Changes are reversible

Key characteristics of chemical changes:

* New substances are formed

* Changes are usually irreversible

* Often accompanied by heat, light, or gas production

Let me know if you have any other questions!