Form 1:
Introduction to Chemistry

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Apparatus for heating/Burners

1. Candle, spirit burner, kerosene stove, charcoal burner/jiko are some apparatus that can be used for heating.

Any flammable fuel when put in a container and ignited can produce some heat.

2. Bunsen burner

The Bunsen burner is the standard apparatus for heating in a Chemistry school laboratory.

It was discovered by the German Scientist Robert Wilhelm Bunsen in 1854.

(a)Diagram of a Bunsen burner

A Bunsen burner uses butane/laboratory gas as the fuel. The butane/laboratory gas is highly flammable and thus usually stored safely in a secure chamber outside Chemistry school laboratory. It is tapped and distributed into the laboratory through gas pipes.

The gas pipes end at the gas tap on a chemistry laboratory bench .If opened, the gas tap releases butane/laboratory gas. Butane/laboratory gas has a characteristic odor/smell that alerts leakages/open gas tap.

The Bunsen burner is fixed to the gas tap using a strong rubber tube.

The Bunsen burner is made up of the following parts:

(i) Base plate: to ensure the burner can stand on its own.

(ii)Jet: a hole through which laboratory gas enters the burner.

(iii)Collar/sleeve: adjustable circular metal attached to the main chimney/burell with a side hole/entry. It controls the amount of air entering used during burning.

(iv)Air hole: a hole/entry formed when the collar side hole is in line with chimney side hole. If the collar side hole is not in line with chimney side hole, the air hole is said to be closed If the collar side hole is in line with chimney side hole, the air hole is said to be open.

(v)Chimney: tall round metallic rod attached to the base plate.

(b)Procedure for lighting/igniting a Bunsen burner

1. Adjust the collar to ensure the air holes are closed.

2. Connect the burner to the gas tap using a rubber tubing. Ensure the rubber tubing has no side leaks.

3. Turn on the gas tap.

4. Ignite the top of the chimney using a lighted match stick/gas lighter/wooden splint.

5. Do not delay excessively procedure (iv) from (iii) to prevent highly flammable laboratory gas from escaping/leaking.

(c)Bunsen burner flames

A Bunsen burner produces two types of flames depending on the amount of air entering through the air holes.

If the air holes are fully open, a non luminous flame is produced. If the air holes are fully closed, a luminous flame is produced. If the air holes are partially open/ closed, a hybrid of non luminous and luminous flames is produced. Characteristic differences between luminous and non-luminous flame

Characteristic differences between luminous and non-luminous flame.

Luminous flame Non-luminous flame
1. Produced when the air holes are fully/completely closed 1. Produced when the air holes are fully/completely open
2. W the air holes are fully/ completely closed there is incomplete burning/ combustion of the laboratory gas 2.When the air holes are fully/ completely open there is complete burning/ combustion of the laboratory gas
3. Incomplete burning/ combustion of the laboratory gas produces fine unburnt carbon particles which make the flame sooty/smoky 3. Complete burning/ combustion of the laboratory gas does not produce carbon particles. This makes the flame non-sooty /non- smoky.
4. Some carbon particles become white hot and emit light. This flame is thus bright yellow in colour producing light. This makes luminous flame useful for lighting 4. Is mainly blue in colour and is hotter than luminous flame. This makes non-luminous flame useful for heating
5. Is larger, quiet and wavy/easily swayed by wind 5.Is smaller, noisy and steady

Luminous flame has three main regions:

(i)The top yellow region where there is incomplete combustion/burning.

(ii)The region of unburnt gas below the yellow region where the gas does not burn.

(iii)Blue region on the sides of region of unburnt gas where there is complete burning.

Non-luminous flame has four main regions:

(i)The top colourless region.

(ii) Blue region just below where there is complete burning. It is the hottest region.

(iii) Green region surrounded by the blue region where there is complete burning.

(Ii) The region of unburnt gas at the innermost surrounded by green and blue regions. No burning takes place here.

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