energy <=

Chemical energies

By virtue of composition, chemical bonding, and state, any material has some chemical energy, whose absolute amount is not a measurable quantity, neither is the quantity useful.

Chemical reactions may be endothermic (requiring energy) or exothermic (releasing energy); so do nuclear reactions.

Food and fuel provide us with chemical energy and perhaps pleasure.

Chemical energy includes, for example:

Energy <=
CHEMICAL ENERGY
4 H + 2 O
Bond energy, 1469 kJ
2 H2 + O2
Combustion energy, 484 kJ
2 H2O(gas) 373 K
Energy of evaporation, 81 kJ
2 H2O(liquid) 373 K
Heat, 15 kJ
2 H2O(liquid) 273 K
Energy of fusion, 12 kJ
2 H2O(solid) 273 K

Food energy (kcal/g) of some food types
Food Heat of
combustin
Physiological
energy
Protein
cheese
beef
5.4 4
4
3
Fat
butter
9.3 9
8
Carbohydrates
potatos
sugar
4.1 4
0.7
4

E-mail: cchieh@uwaterloo.ca