how did the events in Kansas contribute to the onset of the Civil War?

Answer 1

See "The Kansas-Nebraska Act"
http://www.infoplease.com/ce6/history/A0827030.html

This allowed the state of Kansas do let its citizens decide whether is wished to become a pro-slavery state or not. As a result, a murderous period of anarchy broke out within the recenly populated state, which was evenly divided in its sentiments.