Summary: First Law - Closed Systems 
  1. The first law is an energy balance. For a closed system ΔU = Q + W.
  2. Work is done when a gas expands against an external force in a piston-cylinder.
  3. An adiabatic process takes place when the system is well insulated or takes place rapidly. 
                                                                                                                                  https://sites.google.com/a/learncheme.com/learncheme/student-resources/interactive-module-raoult-s-law-and-vapor-liquid-equilibrium/interactive-module-raoult-s-law-intro

Prepared by John L. Falconer and Kimberly R. Bourland

Department of Chemical and Biological Engineering, University of Colorado Boulder