230_Sp10_L06_post-1(1)

# 230_Sp10_L06_post-1(1) - CHEM 230 Sp10 Lecture 06 Chapter...

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CHEM 230 Sp10 Lecture 06 Chapter 6: Δ U q Δ H Session ID: 230

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Systems and U The internal energy (U) of an isolated system is constant. Δ U (change in internal energy) = q + w Energy as work (w) Energy as heat (q) Energy Matter Energy
Surroundings Surroundings: refers to everything except the system In practice, this means that the surroundings is so large that you can treat it as infinite For all systems and surroundings, the heat from or work done on the system is the opposite of the heat from or work done on the surroundings: q surroundings = -q system w surroundings = -w system

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State Function Energy is a state function -it depends only on the state and not how it got there (so are T, P, V)
Concept Question Hiker #1 and Hiker #2 start from the same point on a hill, but take different paths down to the 100 m marker. Hiker #1 takes a path that is 200 m long. Hiker #2 takes a path that is 300 m long. Which of the following would not be a state function? A. Their mass B. The height they climbed C. The force of gravity, g D. The distance they walked E. None of the above

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Concept Question Hiker #1 and Hiker #2 start from the same point on a hill, but take different paths down to the 100 m marker. Hiker #1 takes a path that is 200 m long. Hiker #2 takes a path that is 300 m long. Which of the following would not be a state function? A. Their mass B. The height they climbed C. The force of gravity, g D. The distance they walked E. None of the above
Signs U and q Measure Δ U from perspective of the system. + Δ U = gain energy to system - Δ U = loss of energy from system Measure q from perspective of the system: system Heat out q < 0 (-) Exothermic Heat in q >0 (+) Endothermic

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q and the system? Heat added to a system (q > 0): Temperature up Increases kinetic energy in all forms: translational, vibrational, and rotational OR phase change Adiabatic : no heat exchanged with surroundings q = 0 Isothermal:
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## This note was uploaded on 01/24/2012 for the course PCHEM 230 taught by Professor Gottfried during the Fall '11 term at University of Michigan.

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230_Sp10_L06_post-1(1) - CHEM 230 Sp10 Lecture 06 Chapter...

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