Fire

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion releasing heat’ light and various reaction products. Slower oxidation processes like rusting or digestion are not included by this definition. Fire is hot because conversion of the weak double bond in molecular oxygen O₂, to the stronger bonds in the combustion products carbon dioxide and water releases energy 418 kJ per 33 g of O₂ the bond energies of the fuel play only a minor role here. At a certain point in the combustion reaction called the ignition point flames are produced. The flame is the visible portion of the fire. Flames consist primarily of carbon dioxide water vapor oxygen and nitrogen. If hot enough the gases may become ionized to produce plasma. Depending on the substances alight and any impurities outside the color of the flame and the fire's intensity will be different. Fire has been used by humans in rituals in agriculture for clearing land for cooking generating heat and light for signaling propulsion purposes smelting forging incineration of waste cremation and as a weapon or mode of destruction. Fires start when a inflammable or a combustible material in combination with a sufficient quantity of an oxidizer such as oxygen gas or another oxygen rich compound though non oxygen oxidizers exist is exposed to a source of heat or ambient temperature above the flash point for the fuel oxidizer mix and is able to sustain a rate of rapid oxidation that produces a chain reaction. Where most burning is occurring the fire is white the hottest color possible for organic material in general, or yellow. Above the yellow region the color changes to orange which is cooler then red which is cooler still. The inner core of the candle flame is light blue with a temperature of around 1900 K 1600 °C. That is the hottest part of the flame. The color inside the flame becomes yellow’ orange and finally red. Fire can be extinguished by removing any one of the elements of the fire tetrahedron. Consider a natural gas flame such as from a stove top burner. The ability to control fire was a dramatic change in the habits of early humans. Making fire to generate heat and light made it possible for people to cook food simultaneously increasing the variety and availability of nutrients and reducing disease by killing organisms in the food. The heat produced would also help people stay warm in cold weather enabling them to live in cooler climates. An organized body of people trained and employed to extinguish fires.

Neighbors smelt smoke and called the fire brigade.