Editing Volumetric heat capacity (section)

==Typical values==
The volumetric heat capacity of solid materials at room temperatures and above varies widely, from about 1.2&nbsp;MJ⋅K<sup>−1</sup>⋅m<sup>−3</sup> (for example [[bismuth]]<ref>Based on values in [http://hyperphysics.phy-astr.gsu.edu/hbase/tables/sphtt.html#c1 this table] and density.</ref>) to 3.4&nbsp;MJ⋅K<sup>−1</sup>⋅m<sup>−3</sup> (for example iron<ref>Based on [http://webbook.nist.gov/cgi/cbook.cgi?ID=C7439896&Mask=2&Type=JANAFS&Table=on#JANAFS NIST data] and density.</ref>). This is mostly due to differences in the physical size of atoms. Atoms vary greatly in density, with the heaviest often being more dense, and thus are closer to taking up the same average volume in solids than their mass alone would predict. If all atoms ''were'' the same size, molar and volumetric heat capacity would be proportional and differ by only a single constant reflecting ratios of the atomic molar volume of materials (their atomic density). An additional factor for all types of specific heat capacities (including molar specific heats) then further reflects degrees of freedom available to the atoms composing the substance, at various temperatures.

For most liquids, the volumetric heat capacity is narrower, for example [[octane]] at 1.64&nbsp;MJ⋅K<sup>−1</sup>⋅m<sup>−3</sup> or [[ethanol]] at 1.9. This reflects the modest loss of degrees of freedom for particles in liquids as compared with solids.

However, [[water]] has a very high volumetric heat capacity, at 4.18&nbsp;MJ⋅K<sup>−1</sup>⋅m<sup>−3</sup>, and [[ammonia]] is also fairly high: 3.3&nbsp;MJ⋅K<sup>−1</sup>⋅m<sup>−3</sup>.

For gases at room temperature, the range of volumetric heat capacities per atom (not per molecule) only varies between different gases by a small factor less than two, because every [[ideal gas]] has the same [[molar volume]]. Thus, each gas molecule occupies the same mean volume in all ideal gases, regardless of the type of gas (see [[kinetic theory of gases|kinetic theory]]). This fact gives each gas molecule the same effective "volume" in all ideal gases (although this volume/molecule in gases is far larger than molecules occupy on average in solids or liquids). Thus, in the limit of ideal gas behavior (which many gases approximate except at low temperatures and/or extremes of pressure) this property reduces differences in gas volumetric heat capacity to simple differences in the heat capacities of individual molecules. As noted, these differ by a factor depending on the degrees of freedom available to particles within the molecules.