To explore the feasibility of using hydrogen molecules to probe local surface reactivity, we consider the dissociation dynamics of H₂/Cu₃Pt(111)[1=21], as an example. Calculation results show that as we increase the incidence angle Θ_i (measured with respect to the surface normal) of the impinging H₂, thereby changing the apparent surface features, the corresponding dissociative adsorption/sticking probability S versus incidence translational energy E_t profile changes. Noting that the hydrogen is sensitive to the local features of the solid surface that it is interacting with, and that it distinguishes among them, we were able to account for these results.