* Chemical Change: A chemical change results in the formation of new substances with different chemical properties.

* When zinc reacts with acid (like hydrochloric acid), it forms zinc chloride (a new substance) and hydrogen gas is released.

* The original substances, zinc and acid, are transformed into entirely different substances.

* Physical Change: A physical change alters the form or appearance of a substance but doesn't change its chemical composition. Examples include melting ice or cutting a piece of paper.

Key Indicators of a Chemical Change:

* Formation of new substances: This is the most important indicator.

* Gas evolution: The release of bubbles (like hydrogen gas in this reaction).

* Change in color: The solution might change color.

* Heat or light production: The reaction might release or absorb heat, sometimes producing light.

Therefore, dissolving zinc in acid is a chemical change because it produces new substances (zinc chloride and hydrogen gas).