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The contribution of the muscle to the specific heat of the body is approximately 47%, and the contribution of the fat and skin is approximately 24%. The specific heat of tissues range from ~0.7 kJ · kg−1 · °C−1 for tooth (enamel) to 4.2 kJ · kg−1 · °C−1 for eye (sclera). [13]
In chemistry, heat amounts were often measured in calories. Confusingly, there are two common units with that name, respectively denoted cal and Cal: the small calorie (gram-calorie, cal) is 4.184 J exactly. It was originally defined so that the specific heat capacity of liquid water would be 1 cal/(°C⋅g).
Boltzmann constant: The Boltzmann constant, k, is one of seven fixed constants defining the International System of Units, the SI, with k = 1.380 649 x 10 −23 J K −1.The Boltzmann constant is a proportionality constant between the quantities temperature (with unit kelvin) and energy (with unit joule).
3.3×10 9 J: Approximate average amount of energy expended by a human heart muscle over an 80-year lifetime [140] [141] 3.6×10 9 J = 1 MW·h (megawatt-hour) 4.2×10 9 J: Energy released by explosion of 1 ton of TNT. 4.5×10 9 J: Average annual energy usage of a standard refrigerator [142] [143] 6.1×10 9 J: ≈ 1 bboe (barrel of oil equivalent ...
For example, heats of fusion and vaporization are usually of the order of 10 kJ·mol −1, bond energies are of the order of 100 kJ·mol −1, and ionization energies of the order of 1000 kJ·mol −1. [5] For this reason, it is common within the field of chemistry to quantify the enthalpy of reaction in units of kJ·mol −1. [6]
These tables list values of molar ionization energies, measured in kJ⋅mol −1. This is the energy per mole necessary to remove electrons from gaseous atoms or atomic ions. The first molar ionization energy applies to the neutral atoms.
, , and are the usual agents of a chemical equation with coefficients and is a positive or negative numerical value, which generally has units of kJ/mol. Another equation may include the symbol E {\displaystyle E} to denote energy; E {\displaystyle E} 's position determines whether the reaction is considered endothermic (energy-absorbing) or ...
In general, proteins have lower energy densities (≈16 kJ/g) than carbohydrates (≈17 kJ/g), whereas fats provide much higher energy densities (≈38 kJ/g), [8] 2 + 1 ⁄ 4 times as much energy. Fats contain more carbon-carbon and carbon-hydrogen bonds than carbohydrates or proteins, yielding higher energy density. [ 9 ]