electrochemistry, science dealing with the relationship between electricity and chemical changes. Of principal interest are the reactions that take place between electrodes and the electrolytes in electric and electrolytic cells (see electrolysis), as well as the reactions that take place in an electrolyte as electricity passes through it. The principles of electrochemistry are applied in a variety of ways, e.g., in electroplating and in the generation of electricity by magnetohydrodynamics. See battery; voltaic cell.