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| :''For a table of volumetric heat capacities, see [[Heat capacity#Table of specific heat capacities]].''
| | My name's Mira Buttrose but everybody calls me Mira. I'm from Iceland. I'm studying at the college (2nd year) and I play the Clarinet for 10 years. Usually I choose music from the famous films :D. <br>I have two brothers. I love Videophilia (Home theater), watching TV (Grey's Anatomy) and Mountain biking.<br><br>my weblog :: [http://Sns.Ysten.com/space.php?uid=14668&do=blog&id=55291 homes for sale in sacramento ca] |
| '''Volumetric heat capacity''' ('''VHC'''), also termed '''volume-specific [[heat capacity]]''', describes the ability of a given [[volume]] of a substance to store [[internal energy]] while undergoing a given [[temperature]] change, but without undergoing a [[phase transition]]. It is different from [[specific heat capacity]] in that the VHC is a 'per unit volume' measure of the relationship between thermal energy and temperature of a material, while the specific heat is a 'per unit [[mass]]' measure (or occasionally per molar quantity of the material). If given a specific heat value of a substance, one can convert it to the VHC by [[multiplication|multiply]]ing the specific heat by the [[density]] of the substance.<ref>[http://www.usace.army.mil/usace-docs/armytm/tm5-852-6/c-2.pdf#search=%22%22Volumetric%20heat%20capacity%22%22 ''U.S. Army Corps of Engineers Technical Manual: Arctic and Subarctic Construction: Calculation Methods for Determination of Depths of Freeze and Thaw in Soils'', TM 5-852-6/AFR 88-19, Volume 6, 1988, Equation 2-1]</ref>
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| [[Pierre Louis Dulong|Dulong]] and [[Alexis Thérèse Petit|Petit]] predicted in 1818 {{Citation needed|date=February 2010}} that the product of solid substance density and specific heat capacity (ρc<sub>p</sub>) would be constant for all solids. This amounted to a prediction that volumetric heat capacity in solids would be constant. In 1819 they found that volumetric heat capacities were not quite constant, but that the most constant quantity was the heat capacity of solids adjusted by the presumed weight of the atoms of the substance, as defined by Dalton (the [[Dulong–Petit law]]). This quantity was proportional to the heat capacity per [[atomic weight]] (or per molar mass), which suggested that it is the heat capacity '''''per atom''''' (not per unit of volume) which is closest to being a constant in solids. Eventually (see the discussion in [[heat capacity]]) it has become clear that heat capacities per particle for all substances in all states are the same, to within a factor of two, so long as temperatures are not in the cryogenic range. For very cold temperatures, heat capacities fall drastically and eventually approach zero as temperature approaches zero.
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| The heat capacity ''on a volumetric basis'' in solid materials at room temperatures and above varies more widely, from about 1.2 to 4.5 MJ/m³K{{Citation needed|date=January 2012}}, but this is mostly due to differences in the physical size of atoms. See a discussion in [[atom]]. 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 liquids, the volumetric heat capacity is narrower: in the range 1.3 to 1.9 MJ/m³K{{Citation needed|date=January 2012}}. This reflects the modest loss of degrees of freedom for particles in liquids as compared with solids.
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| 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, due to the fact that in 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]]). 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.
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| ==Gas volumetric heat capacities==
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| Large complex gas molecules may have high heat capacities per mole of gas molecules, but their heat capacities per mole of total gas '''atoms''' are very similar to those of liquids and solids, again differing by less than a factor of two per mole of atoms. This factor of two represents vibrational degrees of freedom available in solids vs. gas molecules of various complexities.
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| In monatomic gases (like argon) at room temperature and constant volume, volumetric heat capacities are all very close to 0.5 kJ/m³K, which is the same as the theoretical value of 3/2 RT per kelvin per mole of gas molecules (where '''R''' is the [[gas constant]] and T is temperature). As noted, the much lower values for gas heat capacity in terms of volume as compared with solids (although more comparable per mole, see below) results mostly from the fact that gases under standard conditions consist of mostly empty space (about 99.9% of volume), which is not filled by the atomic volumes of the atoms in the gas. Since the molar volume of gases is very roughly 1000 times that of solids and liquids, this results in a factor of about 1000 loss in volumetric heat capacity for gases, as compared with liquids and solids. Monatomic gas heat capacities per atom (not per molecule) are decreased by a factor of 2 with regard to solids, due to loss of half of the potential [[Degrees of freedom (mechanics)|degrees of freedom]] per atom for storing energy in a monatomic gas, as compared with regard to an ideal solid. There is some difference in the heat capacity of monatomic vs. polyatomic gasses, and also gas heat capacity is temperature-dependent in many ranges for polyatomic gases; these factors act to modestly (up to the discussed factor of 2) increase heat capacity per atom in polyatomic gases, as compared with monatomic gases. Volumetric heat capacities in polyatomic gases vary widely, however, since they are dependent largely on the number of atoms per molecule in the gas, which in turn determines the total number of atoms per volume in the gas.
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| The volumetric heat capacity is defined as having [[SI]] units of [[joule|J]]/([[cubic metre|m³]]·[[Kelvin|K]]). It can also be described in Imperial units of [[British thermal unit|BTU]]/([[cubic foot|ft³]]·[[Fahrenheit|F°]]).
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| == Volumetric heat capacity in solids ==
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| Since<sup> </sup>the [[bulk density]] of a solid chemical element is strongly related to its molar mass (usually about 3 ''R'' per mole, as noted above), there exists noticeable inverse correlation between a solid’s density and its specific heat capacity on a per-mass basis. This is due to a very approximate tendency of atoms of most elements to be about the same size, despite much wider variations in density and atomic weight. These two factors (constancy of atomic volume and constancy of mole-specific heat capacity) result in a good correlation between the ''volume'' of any given solid chemical element and its total heat capacity. Another way of stating this, is that the volume-specific heat capacity (volumetric heat capacity) of solid elements is roughly a constant. The [[molar volume]] of solid elements is very roughly constant, and (even more reliably) so also is the molar heat capacity for most solid substances. These two factors determine the volumetric heat capacity, which as a bulk property may be striking in consistency. For example, the element uranium is a metal which has a density almost 36 times that of the metal lithium, but uranium's '''volumetric''' heat capacity is only about 20% larger than lithium's.
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| Since the volume-specific corollary of the Dulong-Petit specific heat capacity relationship requires that atoms of all elements take up (on average) the same volume in solids, there are many departures from it, with most of these due to variations in atomic size. For instance, [[arsenic]], which is only 14.5% less dense than [[antimony]], has nearly 59% more specific heat capacity on a mass basis. In other words; even though an ingot of arsenic is only about 17% larger than an antimony one of the same mass, it absorbs about 59% more heat for a given temperature rise. The heat capacity ratios of the two substances closely follows the ratios of their molar volumes (the ratios of numbers of atoms in the same volume of each substance); the departure from the correlation to simple volumes in this case is due to lighter arsenic atoms being significantly more closely packed than antimony atoms, instead of similar size. In other words, similar-sized atoms would cause a mole of arsenic to be 63% larger than a mole of antimony, with a correspondingly lower density, allowing its volume to more closely mirror its heat capacity behavior.
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| ==Thermal inertia==
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| ''Thermal inertia'' is a term commonly used by [[scientist]]s and [[engineers]] modelling [[heat transfer]]s and is a bulk material property related to [[thermal conductivity]] and volumetric heat capacity. For example, ''this material has a high thermal inertia,'' or ''thermal inertia plays an important role in this system,'' which means that dynamic effects are prevalent in a [[model (abstract)|model]], so that a steady-state calculation will yield inaccurate results. | |
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| The term is a scientific analogy, and is not directly related to the mass-and-velocity term used in [[mechanics]], where [[inertia]] is that which limits the [[acceleration]] of an object. In a similar way, thermal inertia is a measure of the thermal mass and the velocity of the thermal wave which controls the surface temperature of a material. In [[heat transfer]], a higher value of the volumetric heat capacity means a longer time for the system to reach [[Thermodynamic equilibrium|equilibrium]].
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| The thermal inertia of a material is defined as the square root of the product of the material's bulk [[thermal conductivity]] and volumetric heat capacity, where the latter is the product of [[density]] and [[specific heat capacity]]:
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| :: <math>I=\sqrt{k \rho c}</math>
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| See also [[Thermal effusivity]]
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| * <math>k</math> is thermal conductivity, with unit [W m<sup>−1</sup> K<sup>−1</sup>]
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| * <math>\rho</math> is density, with unit [kg m<sup>−3</sup>]
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| * <math>c</math> is heat capacity, with unit [J kg<sup>−1</sup> K<sup>−1</sup>]
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| * <math>I</math> has [[SI]] units of thermal inertia of [J m<sup>−2</sup> K<sup>−1</sup> s<sup>−1/2</sup>]. Non-SI units of Kieffers [Cal cm<sup>−2</sup> K<sup>−1</sup> s<sup>−1/2</sup>] also used in older references.<ref>http://scienceworld.wolfram.com/physics/ThermalInertia.html ''Eric Weisstein's World of Science - Thermal Inertia''</ref>
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| For planetary surface materials, thermal inertia is the key property controlling the diurnal and seasonal surface temperature variations and is typically dependent on the physical properties of near-surface geologic materials. In [[remote sensing]] applications, thermal inertia represents a complex combination of particle size, rock abundance, bedrock outcropping and the degree of induration. A rough approximation to thermal inertia is sometimes obtained from the amplitude of the diurnal temperature curve (i.e., maximum minus minimum surface temperature). The temperature of a material with low thermal inertia changes significantly during the day, while the temperature of a material with high thermal inertia does not change as drastically.
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| Deriving and understanding the thermal inertia of the surface can help to recognize small-scale features of that surface. In conjunction with other data, thermal inertia can help to characterize surface materials and the geologic processes responsible for forming these materials.
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| Thermal inertia of the oceans is a major factor influencing [[climate commitment]], the degree of [[global warming]] predicted to eventually result from a step change in [[climate forcing]] such as a fixed increase in the atmospheric concentration of a [[greenhouse gas]].
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| == Constant volume and constant pressure == | |
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| For gases it is necessary to distinguish between volumetric heat capacity at constant volume and volumetric heat capacity at constant [[pressure]], which is always larger due to the pressure-volume work done as a gas expands during heating at constant pressure (thus absorbing heat which is converted to work). The distinctions between constant-volume and constant-pressure heat capacities are also made in various types of [[specific heat capacity]] (the latter meaning either mass-specific or mole-specific heat capacity).
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| ==References==
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| <references />
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| ==See also==
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| *[[Heat Capacity]]
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| *[[Specific Heat Capacity]]
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| *[[Temperature]]
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| *[[Thermal effusivity]]
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| *[[Thermodynamic equations]]
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| {{DEFAULTSORT:Volumetric Heat Capacity}}
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| [[Category:Thermodynamic properties]]
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| [[Category:Physical quantities]]
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| [[Category:Volume]]
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| [[Category:Heat transfer]]
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My name's Mira Buttrose but everybody calls me Mira. I'm from Iceland. I'm studying at the college (2nd year) and I play the Clarinet for 10 years. Usually I choose music from the famous films :D.
I have two brothers. I love Videophilia (Home theater), watching TV (Grey's Anatomy) and Mountain biking.
my weblog :: homes for sale in sacramento ca