CAS CH 112 Lecture Notes - Lecture 2: Isothermal Process, Isolated System, Exothermic Process

• School: Boston University
• Department: Chemistry
• Course: CAS CH 112
• Professor: Binyomin Abrams

Document Summary

U for gas expanding isothermally in a vacuum. External pressure in 0, so work is 0. Isothermal- at the same temperature, so no temperature change, so q=0. U for gas expanding isothermally with external pressure. Consider: if two ideal gasses expand to the same volume, one with an external pressure of 1 atm and the other in a vacuum. U for expansion into a vacuum is 0, and as u is a state function u for expansion against 1 atm of pressure must also be 0. U= 0, but work has to be done to expand against external pressure, so w= -q. For the system to remain at constant temperature, heat must go into the system, as internal energy is lost from the work being done, so q is positive. Heat: energy transferred due to a temperature difference or the flow of energy when no work is done.