A little question about voltage

When electrons came out of the negative side (of the battery) and went into an electrical applicance like motor, then the electrons went back to the positive side (of the battery). What have changed is the potential energy of the electrons. As each of the electrons on the circuit have only moved a very limited distance, but there is a great deal of electrons, each moves only a bit then it seems the whole circuit is moving, in reality it is not. So the speed of electrons travelled in space for a particular direction is fixed. Only the speed of resonance the electrons will changed as the potential energy of the electrons have changed. The number of electrons will never change as no 'matter' is consumed in the process of electricity flowing.
I hope this can help your understanding. :)