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Physics LibreTexts

8.9: Numerical Values of Specific and Molar Heat Capacities

  • Page ID
    8604
  • The following table is not intended as a definitive, authoritative table of precise heat capacities. It is intended just to give a rough idea of the orders of magnitude and the relative magnitudes for a few substances.

    For gases, the heat capacities tabulated are at constant pressure. For solids and liquids the difference between Cp and Cv is much smaller than for gases, because of the much smaller coefficient of expansion. Notice that the molar heat capacities for gases, when expressed in terms of R, are about what are expected from the theoretical considerations in this chapter. Notice the relatively large molar heat capacities of organic liquids (the molecules can rotate and can vibrate in many modes), and that, the more complex the molecule, the larger its molar heat capacity. Notice, however, that, because water has a low molecular weight (molar mass), water has the largest specific heat capacity of any common liquid or solid. (The specific heat capacities of gaseous H2 and He are, unsurprisingly, larger still. A kilogram of hydrogen is an enormous number of molecules, so it takes a lot of heat to warm them all up.) We have not studied the theory of the heat capacities of solids in this chapter, but, when you do so in a course on solid state physics or on statistical mechanics, you will understand that the expected molar heat capacity of metals would be about 3R, which is approximately what is shown for the three metals in this table.

    Specific Heat Capacity at Constant Pressure Molar Heat Capacity at Constant Pressure
    cal g−1−1 J kg−1 K−1 J kmole−1 K−1 In units of R
    Helium (g) 1.25 5250 21000 2.53 R
    Argon (g) 0.13 526 21000 2.53 R
    H2 (g) 3.44 14400 28800 3.46 R
    O2 (g) 0.22 919 29400 3.54 R
    N2 (g) 0.25 1040 29100 3.50 R
    CO2 (g) 0.20 843 37100 4.46R
    H2O (g) 1 4184 75300 9.1 R
    C2H5OH (l) 0.58 2430 112000 13.5 R
    CCl4 (l) 0.20 852 131000 15.8 R
    C6H6 (l) 0.42 1740 136000 16.4 R
    Al (s) 0.22 941 25400 3.1 R
    Cu (s) 0.092 384 24400 2.9 R
    Fe (s) 0.11 450 25100 3.0 R
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