What part of Social Security payments are exempted under a Chapter 7?

Social security disability is different from "regular" social security payments.  They are most likely exempt, but it depends on the laws of whatever state's exemptions apply in your case.  Exemption laws are based on the state where you resided for the 2 years prior to filing your bankruptcy case or, if you lived in more than 1 state during that period, in the state where you resided for the greater part of the 180 days prior to that 2 year period. 

For more on exemptions, see http://www.bklaw.com/exemptions.html