Surface modification has been considered as a fundamental item in upper-division undergraduate and master courses. Thus, the development of experiments regarding processes and characterization of surface-modification phenomena is highly desired. In this article, we propose an electrochemical and computational study of widely used surface-functionalization reactions. Electrochemistry was used as a tool to favor the reactions on a pencil tip, which acted as the electrode. By means of cyclic voltammetry, the reduction of two different precursors of grafting species was characterized. The differences observed in the electrochemical signal for both precursors were rationalized through thermodynamics parameters for the reduction reaction calculated by density functional theory (DFT). A theoretical value can be found with an acceptable error (around 12%) when compared with the electrochemical experimental difference. Consequently, a simple, economic, and complete practical and theoretical exercise is presented as an introduction to the Electrochemistry, Surface Chemistry, and Theoretical Chemistry fields.