* Formation of a new substance: When you mix cornstarch (which is a carbohydrate) with vinegar (which contains acetic acid), the acid reacts with the starch molecules. This reaction breaks down the starch into smaller molecules, creating a new substance.

* Change in properties: The mixture will become more viscous and gel-like. This change in consistency is due to the formation of a new substance with different properties than the original cornstarch and vinegar.

* Irreversible reaction: The reaction between cornstarch and vinegar is not easily reversible. You can't simply separate the cornstarch and vinegar back into their original forms.

Therefore, the change in the mixture is not just a physical change of rearranging molecules but a chemical change where new substances are formed.