My textbook says that an electrochemical cell works because of difference in reduction potential of two metals which cause one to lose electrons and other one to accept them. If a salt bridge is not used then the solutions of the two metals become charged and the reaction proceeds till the difference in reduction potential is cancelled by the difference in potential due to charges. All this theory seems to work well on paper, but it is never really explained why this reaction occurs.
What I mean is suppose you have a copper and a silver half cell. They are connected. The copper part does not know whether it is connected by a silver half cell or sodium have cell and I see no apparent of this information being communicated between the cells, so how does it know whether to get dissolved in the solution or precipitate out of the solution?
The book says that due to the difference in reduction potential, a potential gradient is set up which causes the charge to flow. I agree with this completely yet I am not able to grasp why this physically happens. What force causes to electrons to move from one electrode to the other? Especially when there is no salt bridge, the electrons move from positive electrode to negative electrode, which is completely opposite to anything I know.
I think that there must be some difference in local phenomena in the solution which spontaneously causes electrons to flow without any information being shared between the two electrodes. eg: At first I thought maybe copper having lesser reduction potential than silver would dissolve and precipitate out faster (basically a fast(?) equilibrium) which is completely independent of the other electrode and this difference speed would somehow cause the electrons to flow. I rejected this idea after a while but I still think difference in some sort of local phenomena in a half cell which is completely independent of the other half cell would drive the reaction forward.