The main reason why the South lost was because it lacked industry. The South's economy was built on cotton, not on factories. Therefore, it was not nearly as able to manufacture the things it needed for the war. Because of that, it had to try to get them from abroad.
This brings up a second problem, which was its lack of a strong Navy. The prewar US Navy mainly sided with the North, unlike the Army. This made it so that the North could blockade the South relatively well and prevent it from receiving help from foreign countries.
Finally, the South's confederate system hurt them as well. The states had too much power and so the national government was not really able to tax them enough to fund its war effort. This (along with the other factors mentioned) helped lead to shortages for CSA soldiers of all sorts of things needed to fight the war.
10 to 1 in industrail workers, fewers resources, and different ways of transportaton