SS2 Chemistry Lesson Note on Flames

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FLAMES

Flames are produced when substances burn. A flame is a region where gases combine chemically, with the production of heat and light. The type of flame produced depends on the nature of the substance that is burning. A flame may be luminous (brightly seen and yellow) or non – luminous (barely seen). Types of flame can be explained further using hydrogen, candle and Bunsen flames as examples.

• Hydrogen flame: Hydrogen burns with a very faint, non- luminous flame. The structure is simple, consisting of only regions: the unburnt gas zone and the zone of complete combustion.
• Candle flame: A candle burns with luminous flame four zones can be identified in the flame.
• The zone of unburnt gas around the wick
• The bright yellow luminous zone where there is incomplete burning of the hydrocarbon due to insufficient air supply
• The barely visible, non- luminous zone on the outside where complete of carbon particles take place due to sufficient air supply
• The blue zone at the base of the flame which also a region of complete combustion.

• unsen flame: A Bunsen burner is built with an air inlet of the base of the burner tube so that a stream of air can be supplied to the flame together with the fuel gas.

It is important equipment in a school laboratory used for heating. The fuel for the burner is a mixture of hydrocarbon gas (methane and butane) and some hydrogen and carbon (II) oxide

Luminous Bunsen flame: to produce luminous Bunsen flame, the air hole at the base of the burner tube should be closed. The flame produced is high, bright, wavy and yellow but not hot.

Non- luminous Bunsen flame: To produce non- luminous Bunsen flame, the air hole should be kept open. The flame is much hotter, cleaner and more compact than the luminous Bunsen flame.

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