Answer:
Adding a piece of Zn
Explanation:
Adding zinc (Zn) to a hydrochloric (HCl) solution will prove its acidity with a redox reaction:
[tex] Zn(s) + 2H^+(aq) \longrightarrow Zn^{+2}(aq) + H_2(g)[/tex]
This reaction can be confirmed, by the observation of little bubbles in the surface of the metal: that bubbles are the hydrogen gas generated.
