What occurs when zinc metal is added to hydrochloric acid?
I don't know. It has been years since I did that experiment.
The addition of zinc metal, as a powder, would have produced a vigorous effervescence; heat would also have been evolved. The metal powder would have gone up into solution. We can represent this reaction by the balanced chemical equation:
We write the equation in order to establish the stoichiometry; the mass equivalence of the reactants and product.