Heat 08
Heat 08 : As related to combustion, heat may be manifested in the form of rapid oxidation, with the evolution under certain circumstances, of flame, smoke and light. A knowledge of the conditions that determine whether rapid oxidation of a substance with evolution of light will occur is essential to the principles of fire control and investigation. All substances are made up of atoms or groups of atoms (molecules). Each atom consist of units of energy in the form of electrons, protons, and neutrons in continuous motion --- ultimately expressing individual composition in the form of energy. Energy can be expressed in the form of heat. Chemical reactions are endothermic or exothermic. Exothermic reactions are those which produce products with less total energy than the reacting substance whereupon the energy has been released in the form of heat. Endothermic reactions produce products with more total energy than the reacting substances whereupon energy in the form of heat has been absorbed. Oxidation reactions involved in fires are exothermic in the sense that one of the products of the reaction is heat. While, by far, the most common oxidizing material is the oxygen of the atmosphere (one-fifth oxygen and four-fifths nitrogen), certain chemicals, such as sodium nitrate and potassium chlorate, can also readily release oxygen under favorable conditions thereby supplying the flame environment or even creating an explosive environment. Certain pyroxylin plastics contain sufficient oxygen combined in their molecules to produce combustion without an outside source; zirconium dust may be ignited with carbon dioxide. Other explosive and industrial compounds, as earlier stated, will produce oxidizing conditions sufficient for graduated or instantaneous decomposition accompanied by the disengagement of heat.
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