The concept of free soil helped to bring about the Civil War because it helped to make both North and South unhappy over the issue of slavery.
The concept of free soil simply held that slavery should not be allowed to expand. It believed this not for the sake of the slaves, but for the sake of white farmers. Free soilers believed that the dignity of white men was increased if they could own and work their own land. This was less possible in areas with slavery because large plantations dominated these areas.
With the growth of this ideology, Northerners wanted to contain slavery. The South felt that they were being squeezed and that the North was trying to destroy their way of life. This helped lead to the war.