CHEMISTRY:AIR,COMBUSTION AND FIRE FIGHTING

AIR, COMBUSTION, RUSTING AND FIRE FIGHTING.

AIR

-          This is the colourless mixture of gasses. It is supposed to be colourless and testless.

-          Air is composed of several gases.

In addition to nitrogen air contain oxygen, carbondioxide, water vapour and noble gases.

Gas	Approximate percent
Nitrogen	78%
Oxygen	21%
Noble gas	0.94%
Carbondioxide	0.03%
Water vapour	0-4%

USES OF GASES IN AIR

(A)   NITROGEN.

This gas is present in air in the largest proportional.

It is not directly available to plants and animals. Its presence in the air helps to dilute oxygen.

-          Nitrogen in plants and animals is obtained by indirect methods eg. Nitrogen fixation.

(B)   OXYGEN

All plants and animals need oxygen for breathing. Oxygen is necessary for burning of fuels and rusting, green plants supply oxygen to the air during photosynthesis.

(C)   CARBONDIOXIDE

Sources: Respiration in plants and animals produce carbon dioxide.

-          All fires from burning fuel produce the gas.

-          Auto mobile and all other fuel engine produce carbon dioxide in the exhaust.

Uses: Green plant take carbon dioxide from the atmosphere during photosynthesis they use it to make food (sugar and starch)

-          The gas is used extensively in the fire extinguisher.

(D)   NOBLE GAS.

Argon, Helium, Neon and comprise a family know as noble gases.

Uses.

-          Helium is used to fill certain photographic flash bulbs.

-          Argon is used for filling electric light bulbs. It is the cheapest and most abundant noble gas.

-          Neon is used for filling electric discharge tubes for illumination and for advertising sign.

-          Helium is second to hydrogen as the highest gas known as the gas for filling balloons. It has replaced by hydrogen.

COMBUSTION

-          Combustion is the combination of a substance with oxygen gas in air or pure oxygen.

-          It is accompanied by a liberation of heat and light.

·         Combustion does not necessary involve oxygen. For example, sodium burns in chlorine to term sodium chlorine.

In combustion, one of the reactant must be a gas.

-          The burning of organic substance produce carbon dioxide and water vapour as the main products.

-          Oxygen supply is not enough, combustion becomes not complete and carbon dioxide may be made.

APPLIC ATION OF COMBUSTION.

Area	Application
Industries	-          In engines -          In large boilers -          In incinerator for burning wastes
Domestic	-          Cooking -          Heating homes -          Burning waste
Laboratory	-          Sterilization -          During experiments.

RUSTING

-          Rusting is a chemical process that accurse in iron or steel.

-          The reddish brown coasting on the metals is called rust.

CONDITION FOR RUSTING.

-          Air (oxygen)

-          Water

-          Iron/steel.

METHOD OF PREVENTING RUSTING

The following are the method used to prevent rusting.

1.       PAINTING.

Is the coating of the item with a special pigment paint.

Item that are made of iron are usually painted to make them last lager.

-          The paint normally has trace of zinc which is a non reactive metal.

-           The painting prevents oxygen and water from coming into contact with iron.

2.       OILING

This involves coating of iron with oil same machine parts can not be protected by painting so they are regularly  oiled or leapt in oil.

3.       GALVANIZATION.

Is the process of coating iron or steel with zinc metal that does not rust zinc is expensive and so it  is economically to use.

4.       TIN PLATING.

Is the coating of iron with tin. Tin can actually made of steel but the inside of iron is coated with a thin layer of tin.

·         This makes them suitable for canning of food.

5.       USE OF PLASTICS.

Parts of same machines or instruments and household do not have to be made of steel or iron, they are made of plastics.

This is not only ensures they do not rust but also plastics items are less expensive.

FIRE FIGHTING

-          Fire Is the process of combustion in which combustible materials combines with oxygen and gives off light, heat and flames.

-          Fire fighting Is the process of extinguishing of harmful fires.

CLASSIFICATION OF FIRES AND THEIR APPROPIATE EXTINGUISHERS.

CLASS	BURNING MATERIALS	APPROPIATE EXTINGUISHER
A	Ordinary soli, combustible materials such as paper wood, clothing etc.	-          Use water -          Any type of portable extinguisher except carbon dioxide -          Sand
B	Flammable, liquids such as petrol, kerosene, alcohol etc.	-          Use of blankets or sand for small fires -          Use dry powder foam or carbon dioxide fire.
C	Flammable gases such as butane and propane	-          Dry powder -          Carbon dioxide.
D	Combusting metals such as magnesium, sodium, lithium in powder foam.	-          Dry powder foam extinguisher
E	Electrical equipments	-          Use carbon dioxide or dry powder N:B switch off power.
F	Cocking appliances with oil and fats at high temperature	-          Use wet chemical extinguisher.