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Types of bunsen burner flames and their characteristics

Answer Text:
The Bunsen burner flames.
- A flame is a mass of burning gases.
- A bunsen burner can produce two types of flames depending on the size of the air hole and hence amount of air entering the chimney.
Types of flames:
Luminous flame.
Non-luminous flame.
(a). The luminous flame.
- It is a large bright yellow flame produced when the air hole is closed and hence no air enters the chimney.
Characteristics of a luminous flame.
- It is large, quiet and bright yellow.
- Colour is not uniform and it has four zones.
- It produces less heat.
- It gives a lot of light to the glow of unburnt hot carbon particles
- It produces soot. Diagram: the luminous and non-luminous flame.

Parts of a luminous flame.
-The thin outer zone:
- Is a fairly visible, narrow zone on the outer surface of the flame.
- At this point methane (lab gas) mixes with sufficient air from the outside and burns completely to carbon (IV) oxide and water.
- The inner bright yellow zone:
- It is a large bright yellow zone that lies beneath the thin outer zone.
- Here, air supply is insufficient resulting to incomplete combustion of the gas.
- Consequently the gas burns producing tiny carbon particles instead of carbon (IV) oxide.
- The white hot carbon particles glow brightly and are responsible for the yellow colour and the emission of light.
- On cooling the carbon particles form soot, which blackens the bottom of the apparatus being heated.
- The almost colourless inner zone.
- Is found below the yellow inner zone; and consists mainly of unburnt gases.
- The blue zone (region)
- Is found on the outer side of the base of the flame.
- Here, air near the flame rises rapidly due to convection currents and mixes with the burning gas.
- This makes burning more complete than in the two upper parts above it.
Advantages of the luminous flame:
- Can be used for lighting purposes; because it produces more light.
Disadvantages.
- Produces less heat hence inefficient in heating.
- Due to production of soot it blackens apparatus thus preventing better observations of experiments.
(b). The non-luminous flame.
- It is a small blue flame produced when the air hole is completely open and hence a lot of air enters the chimney.
Characteristics of a nonluminous flame.
- It is small, noisy and blue.
- Colour is uniform and it has three regions.
- It produces comparatively more (a lot of) heat.
- It does not produce soot, due to complete combustion hence no carbon particles remain.
- It produces less light due to lack of white-hot carbon particles.
Diagram: non- luminous flame.
Parts of a non-luminous flame.
The outer pale blue region.
- It is a large light blue zone.
- Here, there is a lot of air coming up the chimney from the air hole and from the outside.
- The air gas mixture thus burns completely to carbon (IV) oxide and water.
- No soot formation because there are no carbon particles.
- The middle green blue
region.
- consists of partially burnt gas-air mixture, due to insufficient air supply.
- However as the mixture rises up the pale blue region, it undergoes complete combustion due to plenty of air (from outside)
-The inner almost colourless region.
- Is located at the base of the flame.
- It consists of unburnt gasair mixture.
Advantages of a nonluminous flame.
- Gives out a lot of heat hence very efficient in hating.
- It does not form soot hence will leave apparatus clean even after experiment (heating).
Disadvantages:
- It uses a lot of laboratory gas in burning.
- cannot be used for lighting purposes since it produces very little light.