Factors that affect specific heat capacity
- Degrees of freedom: Molecules are quite different from the monatomic gases like helium and argon. With monatomic gases, heat energy comprises only translational motions. Translational motions are ordinary, whole-body movements in 3D space whereby particles move about and exchange energy in collisions (like rubber balls in a vigorously shaken container). These simple movements in the three X, Y, and Z–axis dimensions of space means monatomic atoms have three translational degrees of freedom. Molecules, however, have various internal vibrational and rotational degrees of freedom because they are complex objects; they are a population of atoms that can move about within a molecule in different ways (see animation at right). Heat energy is stored in these internal motions. For instance, nitrogen, which is a diatomic molecule, has five active degrees of freedom: the three comprising translational motion plus two rotational degrees of freedom internally. Not surprisingly, nitrogen has five-thirds the constant-volume molar heat capacity as do the monatomic gases.[2] See Thermodynamic temperature for more information on translational motions, kinetic (heat) energy, and their relationship to temperature.
- Molar mass: When the specific heat capacity, c, of a material is measured (lowercase c means the unit quantity is in terms of mass), different values arise because different substances have different molar masses (essentially, the weight of the individual atoms or molecules). Heat energy arises, in part, due to the number of atoms or molecules that are vibrating. If a substance has a lighter molar mass, then each gram of it has more atoms or molecules available to store heat energy. This is why hydrogen—the lightest substance there is—has such a high specific heat capacity on a gram basis; one gram of it contains a relatively great many molecules. If specific heat capacity is measured on a molar basis (uppercase C), the differences between substances is less pronounced and hydrogen’s molar heat capacity is quite unremarkable. Conversely, for molecular-based substances (which also absorb heat into their internal degrees of freedom), massive, complex molecules with high atomic count — like gasoline — can store a great deal of energy per mole and yet, be quite unremarkable on a mass basis
Since the bulk density of a solid chemical element is strongly related to its molar mass, generally speaking, there is a strong, inverse correlation between a solid’s density and its cp (constant-pressure specific heat capacity on a mass basis). Large ingots of low-density solids tend to absorb more heat energy than a small, dense ingot of the same mass because the former comprises more atoms. Thus, generally speaking, there a close correlation between the size of a solid chemical element and its total heat capacity (see Volumetric heat capacity). There are however, many departures from the general trend. 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 energy for a given temperature rise.- Hydrogen bonds: Hydrogen-containing polar molecules like ethanol, ammonia, and water have powerful, intermolecular hydrogen bonds when in their liquid phase. These bonds provide yet another place where kinetic (heat) energy is stored.
All measurements are at 25 °C unless otherwise noted.
Substance Phase cp Cp Cv J g-1 K-1 J mol-1 K-1 J mol-1 K-1 Air (Sea level, dry, 0 °C) gas 1.0035 29.07 Air (typical room conditions) gas 1.012 29.19 Aluminium solid 0.897 24.2 Ammonia liquid 4.700 80.08 Antimony solid 0.207 25.2 Argon gas 0.5203 20.7862 12.4717 Arsenic solid 0.328 24.6 Beryllium solid 1.82 16.4 Copper solid 0.385 24.47 Diamond solid 0.5091 6.115 Ethanol liquid 2.44 112 Gasoline liquid 2.22 228 Gold solid 0.1291 25.42 Graphite solid 0.710 8.53 Helium gas 5.1932 20.7862 12.4717 Hydrogen gas 14.30 28.82 Iron solid 0.450 25.1 Lead solid 0.127 26.4 Lithium solid 3.58 24.8 Magnesium solid 1.02 24.9 Mercury liquid 0.1395 27.98 Nitrogen gas 1.040 29.12 20.8 Neon gas 1.0301 20.7862 12.4717 Oxygen gas 0.918 29.38 Silica (fused) solid 0.703 42.2 Uranium solid 0.116 27.7 Water gas (100 °C) 2.080 37.47 28.03 liquid (25 °C) 4.1813 75.327 74.53 solid (0 °C) 2.114 38.09
Notable minima and maxima are shown in maroon.
I'm expecting a harsh winter, and want to make a decent hand-warmer [;)]
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These water resistant heated gloves are great for hiking, skiing and hunting. The safely concealed heating element in the gloves is designed to warm the upper palm area and radiate out to the finger area. They have a cosy lining for extra warmth which also helps to eliminate heat loss. These would make an fabulous gift for the active outdoor person!
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Water is by far the material with the highest thermal capacity no other solid or liquid comes near.
Although water is a very good heat storage materiel surely the best way to store heat is by means of a liquid to solid phase change.
Again water is very good but it occurs at the inconveniently low temperature of 0°C, what we need is some materiel where this phase change occurs in the 30-50°C region, any suggestions?.
My great grandmother (born 1855) used to recommend a quantity of decayed wood (touch wood) smouldering in a tin can.
It would have to be something that doesn't generate it's ownGiven that the cold hands you want to (re-)warm have a pretty sizeable heat capacity of their own, it seems that using anything based only on its heat capacity would make up for a rather poor, short lasting hand warmer - if not so extremely bulky/heavy that you would not want to carry it around with you.
What element, product or, er, thing best retains heat? It would have to be something that doesn't generate it's own, and it should be a solid.
I'm expecting a harsh winter, and want to make a decent hand-warmer [;)]
Let me just quantify it a bit - if there were a series of these "things" all heated to say 100°C, which would retain the heat the longest?
What material retains heat the best?I vote for space shuttle tiles...
so what temperature are they at then?The narrator says that the bricks have been in an oven at "2200 degrees" but doesn't clarify whether that is Celsius (used by scientists) or Fahrenheit (used by the US public).
how does the visible infra red not burn him ala barbecue ?The outer corners are in contact with air at room temperature, so they cool down very quickly (go dark).