* Chemical Properties: Describe how a substance reacts with other substances to form new substances. They involve changes in the chemical composition of the substance.

* Physical Properties: Describe the characteristics of a substance that can be observed without changing its chemical composition.

When a metal reacts with an acid, a chemical reaction takes place:

* Metal + Acid → Salt + Hydrogen Gas

This reaction forms new substances (salt and hydrogen gas) that have different chemical compositions than the original metal and acid. This change in composition is a defining characteristic of a chemical property.

Examples:

* Zinc reacting with hydrochloric acid: Zinc (Zn) reacts with hydrochloric acid (HCl) to produce zinc chloride (ZnCl₂) and hydrogen gas (H₂). This is a chemical reaction because new substances are formed.

* Magnesium reacting with sulfuric acid: Magnesium (Mg) reacts with sulfuric acid (H₂SO₄) to produce magnesium sulfate (MgSO₄) and hydrogen gas (H₂). This is a chemical change as well.

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