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What is fire made of?Fire is a combination of chemical and physical changes in which substances interact to release heat, light, smoke and ash. Whether it is a fire in electrical insulation, an oil fire or a simple domestic fire, they all require three ingredients – combustible material, oxygen and a thermal trigger.If one of these is absent, the fire goes out. This principle is the basis of fire-fighting, which aims to cool the flames by smothering them, removing oxygen, or depriving them of fuel.Combustible material often consists mainly of carbon and hydrogen and can be almost anything solid, liquid or gaseous, from hydrogen to wax, oil, wood and plastic. Even metal will burn provided the temperature is high enough.Sufficient quantities of oxygen are usually supplied by the air, and the energy to light a fire is produced by friction or sparks.Why will a piece of flint produce sparks?Flint produces sparks because it is so hard. However, pieces of flint are only striking tools, and the sparks themselves come from a sparking material such as pyrite - a compound of iron and sulfur – steel, or a composite metal with iron content.In the Stone Age, a firelighter was often a lump of pyrite, a firestone to strike it on and some dried moss or the tinder fungus sometimes known as touchwood. In medieval pistols, the flint created the spark by striking iron, while in today’s disposable cigarette lighters a friction wheel creates tiny sparks from a composite metal which ignites the flow of gas.Expensive lighters use piezoelectric quartz crystals to produce sparks.Why are candle flames yellow?The colour of a flame is the result of several factors - the temperature of the flame, the chemical composition of the fuel that sustains it and the eye’s ability to perceive it.The predominant yellow colour comes from burning carbon molecules. After the heat has stripped the wax from the wick, the carbon initially clumps together into soot particles, which then burn further up with a bright light fed by oxygen in the air.The presence of some metal atoms in a flame can give rise to a rich range of colours. However, what an observer sees depends partly on the structure of the human eye, which is less sensitive to some colours than others.Reds appear less intense than yellows or greens, and so the flame may appear to be mostly yellow.
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This is interesting science behind the fire...
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