CBSE Class 8 Science – Fuel, Combustion and Flame
Flame – Everything that burns does not produce a flame, substances which vaporize will only produce a flame, wax is a hydrocarbon.
When we light candle with a matchstick, the heat of the burning matchstick melts wax first, then it changes it into wax vapour. The wax vapour mix with air and then catch fire to produce a flame. Wax vapour combines with oxygen producing heat and light. As a result of this oxidation, carbon changes into carbon dioxide. Candle flame is always in a spindle shape. During combustion of hydrocarbon it may burn incompletely. This form soots carbon. There are four types of zone:
Non-luminous zone – The outermost zone of the candle flame is called the non-luminous zone. As It surrounds as the entire flame. The wax vapours in this layer get more oxygen from the air around. With that complete combustion takes place here.
Luminous zone – This is the hottest part of the flame. Inside this zone is a yellow part of the flame called the luminous zone.
Dark zone – The wax vapours cannot get enough oxygen from the air to burn completely, some carbon particles are left unburnt which get hot and glow emitting yellow light. Just around the wick is dark zone. Where is no combustion.
Blue zone – In this area no oxygen is available for the burning to take place. The blue color at the bottom is due to combustion of carbon monoxide.
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