ln23f07 - LECTURE 23. INTERNAL ENERGY Internal Energy To...

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235 Closed : a bomb V is held constant and P changes. Heat flows Isolated : V is constant and the vacuum prevents heat exchange L ECTURE 23. I NTERNAL E NERGY Internal Energy To begin, we need to distinguish concepts of system and state functions more precisely. To investigate the internal energy of the system, we need to think about different ways to create systems experimentally. System + surroundings = universe Thermo studies the flow of energy in all forms between the chemical system and surroundings Open : the way we normally do reactions With constant pressure but change in volume
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236 No external force External force system system In a vacuum V system P ext P ext V system w = - P ext Δ V V system system Open container with P ext = 1 atm - P ext Δ V = w - (1 atm) Δ V= w Work and Internal Energy Work: we have discussed work in thermo as the result of gas molecules expanding against an external force. w = - P Δ V = - Δ nRT But the source of this expression, and its limitations, wasn’t developed--until now: First consider the idea of a gas expansion (change in Δ V of a gas) in the presence or absence of an external pressure Note that P ext even happens in an open container because of the 1 atm of external pressure.
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This note was uploaded on 05/21/2008 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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ln23f07 - LECTURE 23. INTERNAL ENERGY Internal Energy To...

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