chemical reaction is any process that involves rearangent of the molecular or ionic structure of substances. each chemical reaction is characterised by an activation energy required for the reaction to occur ,for the change or rearrangement to take place
now fro combustion of fuel:we provide this energy by spark (heat pulse).now what about electrolysis?just the mode and manner of providing energy is different:instead of talking of activation energy,we talk of activation overpotential,both bring conceptually the same thing.heat energy is replaced by potential difference in rough terms.
so in short ,electrolysis is a chemical change ,just the mode of activation is different that thermally initiated chemical reactions