Quantum state-resolved scattering experiments for methane molecules colliding with a catalytically active nickel surface are compared to scattering from a nickel surface passivated by a single layer of graphene. The vibrational state distribution of the scattered methane is observed to differ dramatically for the two surfaces. Quantum-mechanical inelastic scattering calculations show that these differences are related to the catalytic activity of the surface impact site. Our results demonstrate how inelastic scattering can be used to probe the reactive potential-energy surfaces of molecule-metal systems important to heterogeneous catalysis.