4. assume that the south won and slavery was preserved. what would have happened to slavery when mechanization (the switch from farming almost exclusively with animals and humans to farming with machines) came and large numbers of slaves were no longer needed? explain your answer in sentences.

The south winning would be a huge issue in itself, and if they continued to use slaves when the Industrial Revolution came around, there wouldn't be a need for slaves, and the vast expansion of the slave trade would shrink by a lot- as the US wouldn't need them.
Here's the problem:
If we're going into counterfactual history, we have to keep a lot of things in mind.
Was the Industrial Revolution sparked because there were no more slaves? If they still had slaves, would it not have been necessary to obtain and invent machines?
Would we be the United States? Would be have gone at war again from the North still being against slavery? Keep these things in mind.
Hopefully this helped!