648 Heat Engines, Entropy, and the Second Law of Thermodynamics*P22.39We take data from the description of Figure 20.2 in section 20.3, and we assume a constant specificheat for each phase. As the ice is warmed from –12°C to 0°C, its entropy increases by∆∆∆SdQTmc dTTmcT dTmcTSSif=====⋅°−°FHGIKJFHGIKJ=zzz−iceK273 KiceK273 KiceK273 Kkg 2 090 J kg CKKkg 2 090 J kg CJK26112612610 027 02732610 027 0273261254ln.lnlnn.bgafAs the ice melts its entropy change is∆SQTmLTf=×=0027027332 9..kg 3.33 10 J kgK5ejAs liquid water warms from 273 K to 373 K,∆SmcdTTmcTTiffiFHGIKJ°FHGIKJ=zliquidliquidkg 4186 J kg CJ Kln.ln.37327335 3As the water boils and the steam warms,∆∆SmLTmcTTSvfi=+FHGIKJ=×+⋅°FHGIKJsteam6kg 2.26 10 J kgKkg2010Jkg Cln.n.3733883731642 14The total entropy change is2 54 32 9 35 3 164 2 14236....++++=afJK .We could equally well have taken the values for specific heats and latent heats from Tables 20.1 and
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .