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OXYGEN IS NEEDED

FOR COMBUSTION

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Combustion is commonly known as burning

Combustion (burning) is the chemical reactionwhich takes place when a substances (fuel)

combines with O2to give out heat and light

energy. O2supports combustion.

Combustion does not take place in the absence

of O2 Substances which undergo combustion are

called fuels.

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The conditions for combustion

Combustion will only take place under the

following conditions :

I Oxygen is present

II Fuel is present

III Enough amount of heat is present

Combustion will not take place if any of these

conditions is not present.

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THE FIRE TRIANGLE

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The products of combustion

Air contains O2 which supports combustion.

This reactive O2 will act on the fuel when a

little heat is provided.

Fuel is a substances which can burn. For

example;

a) Carbon- coal, charcoal, firewood

b) Hydrocarbon- diesel, kerosene, candle,

natural gas.

Hydrocarbon is a compound which contains

2 elements, hydrogen and carbon

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The product of combustion depends on the

kind of fuel burned.

Generally, combustion produces oxidecompound, heat energy and light energy.

The products of fuel combustion :

- The combustion of carbonCO2, heatenergy and light energy.

CARBON + OXYGEN CARBON DIOXIDE +LIGHT ENERGY + HEAT ENERGY

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- The combustion of hydrocarbonCO2, water,

heat energy and light energy.

During the combustion of hydrocarbon, the

hydrogen element combines with oxygen in

the air to form water, while the carbon elementcombines with oxygen to form carbon dioxide.

HYDROCARBON + OXYGEN CARBON DIOXIDE +

WATER + LIGHT ENERGY + HEAT ENERGY

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The water formed can be tested with,

a) Anhydrous copper sulphate solid.

The presence of water will change its colourfrom white to blue.

b) Dry cobalt chloride paper

The presence of water will change its colour

from blue to pink.

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Activity 1: To test for the product of

combustion of charcoal (carbon)

Procedure

- A piece of charcoal washeated using a bunsen

burner .- The smoke released by

the burning charcoalwas collected in a test

tube.- Some lime water was

added into the test tube.

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Observation

The lime water turns cloudy

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Activity 2: To test for the products of

combustion of kerosene (hydrocarbon)A. To test for CO2

Procedure

- The smoke given out by

a lighted kerosene lamp

was collected in a testtube.

- Some lime water was

poured into the test tube.- The test tube was shaken

and any change to the

lime water was observed

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Observation

The lime water turns cloudy

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B. To test for water

Procedure

- A 500 ml beaker wasinverted over a kerosene

lamp.

-

The droplets of liquidformed on the inner

surface of the beaker

were tested with a piece

of blue cobalt chloridepaper

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