How did the fugitive slave act and the kansas Nebraska act increase tensions between the north and the south?

The Fugitive Slave Act was meant to be a gesture of support for the South, in return for them agreeing that the first coast-to-coast railroad could pass through Chicago instead of New Mexico, as they had hoped. It outraged the North - not just Abolitionists, but ordinary citizens who were now obliged to report anyone who looked as though they might be a runaway, on pain of a heavy fine.

The Kansas-Nebraska Act was a hopeful attempt to put the slavery question to the voters of each individual territory, as it came up for admission to the USA. But clearly the states would be admitted one at a time, and this would give the bully-boys a chance to descend on each state in turn, to cause maximum mayhem. It led to 'Bleeding Kansas', often viewed as the curtain-raiser to the Civil War.