584 Heat and the First Law of ThermodynamicsP20.19QmcTmL==CuCuNvapN22∆ej1 0029377 348 00 414....kg 0.092 0 cal gCCcal gkg⋅°−°==bgafbgmm*P20.20The original gravitational energy of the hailstone-Earth system changes entirely into additionalinternal energy in the hailstone, to produce its phase change. No temperature change occurs, eitherin the hailstone, in the air, or in sidewalk. ThenmgymLyLg===×⋅FHGIKJ=×3 33109 8113 401054...J kgm skg msJm222P20.21(a)Since the heat required to melt 250 g of ice at 0°C exceedsthe heat required to cool 600 g ofwater from 18°C to 0°C, the final temperature of the system (water + ice) must be 0°C.(b)Let mrepresent the mass of ice that melts before the system reaches equilibrium at 0°C.QQmLmcTmmfwwicoldhotCJ kgkgJ kgCCCg, so the ice remainingggg= −= −°−×= −⋅°°−°==−=03 33100 6004 186018 01362501361145bgejb
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