# 23-09-10 - in internal energy Delta u = q + w Is always...

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Thursday, September-23-10 - 1 st law in thermodynamics o Internal energy (U) of an isolated system is constant Perfect world scenario not realistic in the real world In actuality not in an isolated system energy is transferred to the surroundings o U is a thermodynamic state function U = f(P,V,T,%) U is a function of (the different units listed) Delta U = q(heat transfer) + w( work ( displacement of matter, volume change)) o What is work? W = -P * Delta V Pressure external to system Delta V = volume change of system o Units of work and energy Work = force x distance = Kg*m 2 *s -2 Work can also equal pressure x volume change which result in the same unit as the one listed above Kg*m 2 *s -2 = J( Joule) 4.184 joules = 1 cal(calorie) (Kj,Kcal applicable) o Transformation at constant volume Delta U = q+ w = q – p(delta)v Delta v = 0 heat exchange during transformation at constant volume is equal to the change

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Unformatted text preview: in internal energy Delta u = q + w Is always applicable you can always right that down when doing questions with thermochemistry o Transformation at constant pressure Look at slide page 17- rearranging and subbing into result in different equations Define state function • Enthalpy H= U + PV qP = delta h • The heat exchanged during a transformation at constant pressure is equal to the change in enthalpy A gas sample does work so it gives off joules and thus we would put this in a negative value – 100 j • Heat s received so we add heat to the system so then therefore -100 + 10 o-90 is the value of the answer o Under page 19 question There will be no change in volume of the gas mixture so there for the work is equal to 0. The reason we came up with this conclusion is because the amount of moles is the same o...
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## This note was uploaded on 10/22/2010 for the course PHYSICS 1D03 taught by Professor N. mckay during the Spring '08 term at McMaster University.

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23-09-10 - in internal energy Delta u = q + w Is always...

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