Why are there different specific heat values given for water? Are they average s
ID: 2034117 • Letter: W
Question
Why are there different specific heat values given for water? Are they average specific heat for a given tempertature range. i.e. from the table why does it take 4.19kJ/kg K to reach 75 celecuis, however 4.22kJ/kg K to reach 100 celecius. If 0-75 degrees is 4.19kJ/kg K shouldn't only the last 25 celecuis i.e. 75-100 celecius be at the higher 4.22kJ/kg K value?
PROPERTY TABLES AND CHARTS TABLE A-3 Properties of common liquids, solids, and foods (a) Liquids Freezing data Liquid properties Boiling data at 1 atm Normal Latent heat of oling vaporization Freezing of fusion Temperature, Density Latent heat Specific Substance point, °C kJ/kg point, °C h, kJ/kg oC 1357 322.4 682 665 639 602 1394 879 Ammonia 33.3 0 161.6 394 185.9 189.3 -185.6 on Benzene Brine (20% sodium chloride by mass) n-Butane Carbon dioxide Ethanol Ethyl alcohol Ethylene glycol Glycerine 80.2 103.9 -78.4 230.5 (at O°C) 385.2 56.6 0 298 783 789 1109 1261 0.59 78.2 838.3 855 800.1 974 179.9 200.6 -268.9 -252.8 22.8 445.7 367.1 251 294.7 510.4 -268.9 -252.8 146.2 22.8 -259.2 Hydrogen Isobutane Kerosene 70.7 593.8 820 10.0 105.7 204-293 356.7 161.5 -38.9 182.2 25 13,560 0.139 423 301 787 809 596 703 Methane 58.4 Methanol Nitrogen 2.55 -195.8 198.6 25.3 -195.8 Octane 306.3 -218.8 Oxygen Petroleum Propane 212.7 230-384 427.8 640 2.25 0 50 50 529 449 1443 1374 1295 1207 1000 Refrigerant-134a 217.0 1.23 1.27 0 Water 333.7 0 988 975 958Explanation / Answer
In the given table, some values are isochroic heat capacity of water and some values are isobaric heat capacity of water. The heat capacity is given at varying temperatures (°C and °F) and at water saturation pressure (which for practicle use, gives the same result as atmospheric pressure at temperatures < 100 °C (212°F)).
The table just gives values to be used for a specific temperature range.
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