We report on in-situ electrochemical stress measurements of well-defined surfaces during electrochemical reactions in aqueous media. Electrochemical stress measurements during hydrogen evolution reaction (HER) on Pt surfaces shows distinct pH-dependent features which we assign to anion adsorption/desorption and hydrogen adsorption/desorption. Our surface stress analysis shows higher hydrogen induced stresses at alkaline environments than stresses observed at acidic pHs. This observation is consistent with the monotonic change in apparent hydrogen binding energy with pH, most likely due to the changes in water interactions with surface. However, H-induced surface stress shows a dramatic increase around neutral pH. We will present our analysis of how interfacial water may explain this effect. Additionally, we will show how in-situ underpotential deposition of Cu on Pt and Ni on Au changes Had induced effects on these surfaces.We will also discuss the structural and compositional evolution of Sr2Fe2O6-δ thin films during oxygen evolution reaction (OER). Interestingly, in-situ electrochemical stress measurements show a tensile stress response during OER which is different from Au model surfaces. We will present our analysis of how potential controlled formation of iron (oxy)hydorxides may explain in-situ stress response and structural evolution of perovskite type structures during OER.In summary, our analysis shows how adsorbate-induced effects can be used to explain surface reactions, and particularly explain and provide insight into interfacial structural changes and water interactions at different pHs.