* New substances are formed: When steel (an alloy of iron and other elements) reacts with an acid (like hydrochloric acid), it undergoes a chemical reaction. The iron in the steel reacts with the acid to form iron ions (Fe²⁺) and hydrogen gas (H₂). This is a clear indication of new substances being formed.

* The composition of the steel is altered: The original steel is no longer present, as the iron has been transformed into iron ions. This means the chemical composition of the material has fundamentally changed.

* The reaction is irreversible: The reaction between steel and acid is not easily reversed. You can't simply separate the iron ions and hydrogen gas to get back the original steel.

In summary, the process of dissolving steel in acid results in the formation of new substances with different chemical properties. This demonstrates that a chemical change has occurred.