Final answer:
Chemical change is evidenced by hydrogen gas bubbling, heat production, and the formation of new substances like zinc chloride when zinc reacts with dilute hydrochloric acid. The balanced chemical equation is Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g).
Step-by-step explanation:
To prove that a chemical change has taken place when zinc granules react with dilute hydrochloric acid (HCl), consider the following observations and experiment. When you place a few drops of dilute hydrochloric acid onto zinc granules, the immediate bubbling indicates the release of hydrogen gas (H2), showing that a new substance is being formed. Additionally, the solution heats up due to the exothermic nature of the reaction, providing further evidence that a chemical change is occurring.
The reaction between zinc (Zn) and hydrochloric acid can be represented by the balanced chemical equation: Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g). To confirm chemical change, detecting the presence of zinc chloride in solution as colorless Zn2+ ions and Cl ions establishes that the reactants have turned into different substances. Moreover, by determining the mass of reactants before and after the reaction, a change in mass resulting from the release of hydrogen gas signifies that a chemical reaction has taken place.