Is it possible to create a galvanic cell without a half cell?
In the book I was reading, Illustrated Guide to Home Chemistry Experiments, the following lab (Laboratory 16.4) was suggested:
add 2M HCl and add copper metal to one end of the beaker, with magnesium at the other end. Then, add patch cables to connect the metal plate to an LED to have physical evidence of success.
However, I don't understand how useful work could be generated without half cells.
To my understanding, we add HCl to react with the magnesium and copper, to produce ions (Cu+ and Mg2+). Then, they can spontaneously produce work due to their eV differences.
What I am missing is how the work can be useful, as opposed to just generating heat in the solution.
I would believe that, rather than traveling though the patch cables, electrons can travel directly through the solution and produce heat.
Thanks for reading and I really appreciate any help!