Explain, in terms of activity, why hcl(aq) reacts with zn(s), but hcl(aq) does not react with cu(s).

Despite the fact that, both Cu and Zn are solid, there is a salient difference among them. In the periodic table, Zinc locates above the H2, so it's more active than the hydrogen, but Copper locates below the Hydrogen, so it's less active. That's why, HCl (aq) reacts with Zn (s) -- more active one, but does not react with Cu (s).