When an electric current is passed through an electrolytic cell, how can we recognise that electrolysis is taking place?

when electric current is passed through an electrolytic cell we can recognise that electrolysis is taking place by :

*there may bubbles of different gases formed on the electrodes.

*if we add vinegar or lime juice we find more bubbles forming

by the we can identify

particle   p is an electron and particle q is a neutron