Uses of Sulphuric Acid
Sulphuric acid is very important industrially, and has many uses including:





the production of fertilisers such as ammonium sulphate, potassium sulphate,
calcium superphosphate (Ca(H<2PO4)2), etc.; these are straight fertilisers, as they
supply one of the important elements of nitrogen, phosphorus, or potassium
(NPK);
the manufacture of non-soapy detergents: modern detergents are organic
compounds 'sulphonated' with concentrated sulphuric acid;
the making of artificial silks like rayon: here, the fine threads in the alkaline
cellulose solution are neutralised by passing them through a bath of sulphuric
acid;
the cleaning of metals by removing the surface oxide coating: this is called
pickling and is important in preparing articles for electroplating.
its use as an electrolyte inside batteries for cars: most car batteries are made up of
lead plates in a sulphuric acid electrolyte; occasionally, the electrolyte needs to be
'topped up' with distilled water ; this is because small amounts of hydrogen and
oxygen gases are given off by the chemical changes inside the battery, and
therefore the sulphuric acid loses water and becomes too concentrated ; in the
manufacture of drugs, paints, dyes and many other chemicals .
Manufacture of Sulphuric Acid: The Contact Process

The large-scale manufacture of this acid is extremely important as it is the most
common acid used in industry, with over 1 000 million metric tonnes being
produced annually.
It is manufactured by the Contact Process.
Stage 1
Combustion of Sulphur sulphur + oxygen sulphur dioxide
S (s) + O2 (g) ---> SO2 (g) or
Heating of metal sulphide such as lead(II) sulphide 2PbS(s) + 3O2(g) ---> 2PbO(s) +
2SO2(g) or Combustion of hiydrogen sulphide 2H2S(g) + 3O2(g) ---> 2SO2(g) +
2H2O(ce)

The raw materials are sulphur and air (oxygen). Sulphur dioxide is produced by
burning either sulphur or ores which contain sulphur.

Purification of sulphur dioxide
1. The sulphur dioxide is then purified, by removing impurities like arsenic
compounds which would otherwise poison the catalyst.
2. It is then passed through an electrostatic dust precipitator, which, as its name
implies, charges dust particles which are then removed by being attracted to
oppositely charged plates.
Stage 2
Formation of Sulphur trioxide sulphur dioxide + oxygen ---> sulphur trioxide 2SO2 (g) +
O2 (g) ---> 2SO3 (g)
Catalyst: vanadium(V) oxide
Temperature: 450°C
Pressure: 2-3 atmospheres



Sulphur dioxide and air are then washed, dried and passed over a vanadium(V)
oxide catalyst at 450°C and 2-3 atmospheres.
The reaction is reversible but at these temperatures and pressures, 98% conversion
to sulphur trioxide is achieved:
This reaction is exothermic, which means it favours a low temperature for high
conversion to sulphur trioxide.
Stage 3
Formation of oleum H2S2O7
sulphur trioxide + concentrated sulphuric acid ¾¾®oleum SO3(g) + H2SO4(aq) --->
H2S2O7(l)

The next step is to dissolve the sulphur trioxide produced in concentrated
sulphuric acid, to form oleum, or fuming sulphuric acid.
Stage 4
Formation of Sulphuric acid Oleum + water ---> sulphuric acid H2S207 (1) + H2O (1) --->
2H2SO4(aq)


This oleum is then diluted with water to the required strength of acid:
Although this may seem a roundabout route to take to form the acid, it is
necessary because sulphur trioxide cannot be dissolved directly in water as it
reacts too violently, forming tiny droplets of sulphuric acid which are very
difficult to remove.
[Sulphur Dioxide as pollutant

Sulphur dioxide (SO2) is the pollutant primarily associated with acid rain.



Gaseous at normal temperature and pressure it dissolves in water and readily
oxidises to sulphuric acid.
Levels of SO2 have reduced over recent years with a move away from widespread
burning of coal in homes and factories.
It is one of the main pollutants that led to the introduction of legislation governing
atmospheric pollution such as the 1956 Clean Air Act.
Sources of Sulphur Dioxide



The principal source of SO2 is from the combustion of fossil fuels in domestic
premises and , more importantly, non-nuclear power stations.
Fossil fuel burning power stations account for around two thirds of total SO2
emissions in the UK.
Other industrial processes contribute a further 20%, with vehicles, primarily
diesel, accounting for a mere 2%.
Health effects


SO2 is an irritant when it is inhaled and at high concentrations (over 1000ppb)
may cause severe problems in asthmatics such as narrowing of the airways,
known as bronchoconstriction.
Asthmatics are considerably more sensitive to the effects of SO2 than other
individuals and an effect on lung function may be experienced at levels as low as
200ppb.
9.2Uses of ammonia
Table 3 Uses of ammonia
Use of ammonia
Percentage
fertilizers
75
nitric acid
10
solvents
8
nylon and other organic compounds 7
Manufacture of Fertilizers



The main use of ammonia is in the manufacture of fertilizers.
Approximately 75% of all ammonia produced is converted into various
ammonium compounds like ammonium sulphate (NH4)2SO4, ammonium nitrate
NH4NO3, ammonium phosphate (NH4)3PO4 and urea NH2CONH2.
These compounds are called nitrogenous fertilizers.
Example
Ammonium sulphate (NH4)2SO4
H2SO4(aq) + 2NH3(aq) --->(NH4)2SO4(aq)
Ammonium nitrate NH4NO3
HNO3(aq) + NH3(aq) ---> NH4NO3(aq)
ammonium phosphate (NH4)3PO4
H3PO4(aq) + 3NH3(aq) ---> (NH4)3PO4(aq)
Urea NH2CONH2
CO2(g) + NH3(g) ---> CO(NH2)2(p) + H2O(l)


They are solids for ease in handling and water soluble so that they seep into the
soil to be absorbed by the roots of the plant.
Nitrogen is an essential element for healthy plant growth as we saw earlier with
the nitrogen cycle. Nitrogen is essential for making proteins which are needed for
healthy growth of stems and leaves. The proportion of nitrogen present in a
particular fertiliser can be calculated and is usually quoted as an 'N' value on the
fertiliser bag.
Solvent Uses




queous ammonia is used as a degreasing agent, as it is a good solvent of grease
and fat.
Many household cleaners boast of the 'power of ammonia' for removing grease
stains around the kitchen.
However, it is wrong, as stated in some commercials, to talk of 'liquid ammonia'.
It is more accurate to say 'ammonia solution', as ammonia does not liquefy until a
temperature of -34 °C is reached.
Characteristic of ammonia
React with acid to form salt and water
As an alkali, ammonia can react with acid to form salt and water.
Example
H2SO4(aq) + 2NH3(aq) ---> (NH4)2SO4(aq)
HNO3(aq) + NH3(aq) ---> NH4NO3(aq)
H3PO4(aq) + 3NH3(aq) ---> (NH4)3PO4(aq)
Ammonia solution react with positive ions
Ammonia dissolve into water to form ammonium and hydroxide ion.
NH3 + H2O ---> NH4+ + OHThe hydroxide ion can react with many kinds of positive ion to form precipitate.
Example
Mg2+ + 2OH- ---> Mg(OH)2
Fe2+ + 2OH- ---> Fe(OH)2
Al3+ + 3OH- ---> Al(OH)3
Testing for Ammonia Gas



Ammonia is the only common alkaline gas, so it can be identified with moist red
litmus paper turning blue.
However, a more specific chemical test is to hold close to the suspected ammonia,
a glass rod dipped into some concentrated hydrochloric acid.
This will give off fumes of hydrogen chloride gas which, in the presence of
ammonia, form a dense, white 'smoke' of ammonium chloride:
ammonia gas + hydrogen chloride gas ---> ammonium chloride
NH3 (g) + HC1 (g) ---> NH4C1 (s)

In the same way, mixing a gas jar of hydrogen chloride and ammonia gas
produces the same dense, white smoke. The smoke again is the fine-particled
solid called ammonium chloride.
The Haber Process
The reaction

Ammonia is made by the Haber process from nitrogen and hydrogen:
N2(g) + 3H2(g) ---> 2NH3(g); Heat of reaction = -92 kJ mo1-1

The reaction is exothermic, and involves a decrease in the number of moles of
gas.
Sources of the raw material
Hydrogen
Hydrogen is produced industrially from cracking oil
Nitrogen
Nitrogen from liquefaction of the air
Condition
Catalyst
Iron
Promoter
Aluminium oxide
Ratio of Hydrogen
and Oxygen
The two gases are combined directly in a ratio of 3 : 1
At 450 °C


Temperature

An application of Le Chatelier's shows that the forward
reaction should be assisted by a low temperature.
At low temperature, the rate of attainment of equilibrium is
low. At high temperature, the position of equilibrium is over
to the left.
A compromise temperature is adopted, and a catalyst is
employed to speed up the attainment of equilibrium
concentrations.
At 200-1000 atm
Pressure

An application of Le Chatelier's shows that the forward
reaction should be assisted by a high pressure.
Products

The yield is about 10%, and unreacted gases are recycled
When the ammonia has been produced, it is liquefied 'out', by reducing the temperature to
-34°C (239 K)
The Manufacture of Nitric Acid (Ostwald Process)
Introduction
Industrially, nitric acid is made by the catalytic oxidation of ammonia over heated
platinum. Oxidising ammonia produces oxides of nitrogen which can then be dissolved in
water to produce nitric acid.
Reaction

Initially, nitrogen(II) oxide will be formed from the catalytic oxidation of
ammonia using the transition metal platinum.
ammonia + oxygen ---> nitrogen(II) oxide + steam
4NH3 (g) + 5O2 (g) ---> 4NO (g) + 6H2O (g)

The nitrogen(II) oxide is rapidly cooled before combining with oxygen (from
excess air) to form nitrogen(IV) oxide.
2NO (g) + O2 (g) ---> 2NO2 (g)

The nitrogen(IV) oxide, mixed with excess air, is then allowed to react with water
to form nitric acid.
nitrogen(IV) oxide + oxygen (air) + water ---> nitric acid
4NO2 (g) + O2 (g) + 2H2O (1) ---> HNO3 (aq)
Uses of Nitric Acid


Most of the nitric acid made is used to make the all-important fertilisers, such as
ammonium nitrate.
Other uses of nitric acid include making explosive, like nitroglycerine, or TNT
(trinitrotoluene), and making dyes. Modern dyes are azo dyes, which can be
formed by the reduction of various nitro-compounds.
9.3Introduction

An alloy is a mixture of two or more metals mixed in a certain percentage.
Characteristic of metal

A pure metal has the following characteristics:
1.
2.
3.
4.
5.
Ductile – can be drawn into wires
Malleable – can be made into sheets
High melting and boiling points
High density
High electrical conductivity









Many metal are also soft. Metals like iron and copper also form oxides easily.
As a result, the uses of pure metals are limited, and alloys are made to improve
the malleability, ductileness and hardness of a metal.
A pure metal is composed of layers of atoms which are arranged in an even,
orderly and close manner at fixed positions (see Figure 9.8). Each atom is
surrounded by 8-12 atoms.
This arrangement of atoms causes the metal to be very dense with high melting
and boiling points. The strong forces of attraction between atoms require a great
amount of heat to overcome.
However, in spite of strong forces of attraction between atoms, the metal is not
hard. If a force is applied on the metal, the layers of atoms can glide and slide on
top of each other, causing them to move to new positions. This allows the metal to
be drawn into wires (ductile). (See Figure 9.9.)
The spaces left naturally between layers of metal atoms also make it easy to be
beaten into sheets (malleable).
The formation of alloys occurs when these empty spaces between metal atoms are
filled with atoms of another metal, which may be higher or smaller than the
original metal atoms. (Figure 9.10)
The foreign atoms are usually another metal but sometimes a non-metal, like a
carbon or silicon is used.
The foreign atoms filling up the spaces between the atoms of the pure metal help
to prevent the slipping and sliding of atom layers, thus making the metal harder,
and less malleable and ductile.
Purpose of Making Alloys

Alloys are made to
1. increase the hardness of metals.
2. prevent the corrosion of metals.
3. improve the beauty and lustre of metals.
Hardness of metals:



Alloys improve the strength of metal.
Carbon is added to iron to obtain steel to make it stronger and harder than pure
iron. Other metals like manganese, chromium and tungsten are also added to add
to the hardness.
Magnalium is made from aluminium and magnesium to improve the hardness of
the pure metals but at the same time, maintaining their lightness.
To prevent corrosion of metals:



Tin and iron are used vastly in building but they rust easily, thereby causing
economical loss. Adding other metals or non-metals to them can prevent rusting.
Stainless steel is made by adding carbon, chromium and nickel to iron.
Adding phosphorus to bronze also improves the lustre and prevents corrosion of
bronze.
Beauty and lustre of metals:



Making alloys also improve the beauty and lustre of metals. They are thus used as
decorative items as they do not tarnish easily.
Stainless steel is used to make forks and spoons.
Copper and antimony added to tin produces pewter, used to make decorative
items.
Alloy
Cupronickel
(Coins)
Composition, Characteristic, and Uses of Alloy
Composition
Properties
Uses
Cu 75%
Hard, strong, resists
Coins
Ni 25%
corrosion
Duralumin
Al 95%
Cu 4%
Mg 1%
Light, strong
Aeroplane parts, electric cables,
racing bicycles
Steel
Fe 99%
C 1%
Hard, strong, cheap
Vehicles, ships, bridges,
buildings
Stainless steel
Fe73%
Cr 18%
Ni 8%
C 1%
Hard, rust resistant
Cu 90%
Sn 10%
Hard, strong, shining
Bronze
Kitchen appliances, watches,
machine parts,
knives, forks, spoons
Decorative items, medals,
artwork, pots and pans
Decorative items, electrical
appliances, musical
Cu 70%
Zn 30%
Harder and cheaper
than Cu
Snider
Pb 50%
Sn 50%
Low melting point,
strong
Welding and soldering work
Pewter
Sn 91%
Sb 7%
Cu 2%
Malleable, ductile,
rust resistant
Decorative items, souvenirs
Magnalium
Al 70%
Mg 30%
Light, strong
Tyre rim of racing cars, skeletal
body of aeroplanes
Brass
instruments, bell, nails, screw,
pots
9.4 Introduction


Polymer is a large molecule that is in the form of a long chain with a high relative
molecular mass (RMM).
It is made up of many smaller units called monomers, which are joined together
through a process called polymerisation. Thus the monomer is actually the
repititive unit of a long polymer chain.
picture

There are two types of polymers:
1. Natural polymers
2. Synthetic polymers
Natural Polymers

These occur naturally in living things. Some examples of natural polymers are:
1. Natural rubber
2. Protein in meat, leather, silk, hair and fur
3. Carbohydrates in cellulose, starch and sugar


Natural polymers are made up of carbon, hydrogen, nitrogen and oxygen.
Natural rubber comprises the molecules of the monomer 2-methyl-1,3-butadiene,
also called isopropene, joined together to form a long chain, as in:
picture

Protein is obtained by the combination of amino acid molecules which represent
the monomer units.
picture

Carbohydrates are formed through the combination of glucose molecule which act
as the monomer.
picture
Synthetic Polymers




Synthetic polymer is a polymer that is manufactured in industry from chemical
substances through the polymerisation process. Through research, scientists are
now able to copy the structure of natural polymers to produce synthetic polymers.
Plastics, synthetic fibres and elastomers are examples of synthetic polymers.
The raw materials for the manufacture of synthetic polymers are distillates of
petroleum.
The two types of polymerisation are:
1. polymerisation by addition
2. polymerisation by condensation

Polymerisation by addition involves monomers with >C = C< bonding, where the
monomers join together to make a long chain without losing any simple
molecules from it. Examples of polymers produced through this process are
polythene, PVC perspex and other plastics.

Polymerisation by condensation involves the elimination of small molecules like
water, methanol, ammonia or hydrogen chloride during the process. Examples of
products of this process are terylene and nylon-66.
Plastics

Plastics are light, strong and do not react with any chemical substances, like acids
and alkalis. They can be made into many shapes and sizes. They are also good
insulators of heat and electricity.
Plastics (Addition )
Polythene (polyethylene)
Structure
Uses
Plastic bags, containers and cups
picture
–light; cannot tear easily
Polyvinyl chloride or
PVC(polychloroethene)
Polystyrene(polyphenylethene)
raincoat, pipes, to insulate electric wires
picture
–can be coloured; heat resistant
picture
Packaging materials, children toys, ballpoint pens, as heat and electric
insulators
– light and strong
Aeroplane window panes, lenses, car
lamp covers
Perspex (polymethyl2-methyl
propene)
picture
Polypropene
picture
–light, strong, translucent, stable
towards sunlight
Plastics, bottles, plastic tables and chairs
–strong and light
To make non-stick pots and pans
Teflon(polytetrafluoroethene or
PTFE)
picture
–hard, can withstand high temperatures
and corrosives chemicals
Synthetic rubber


Synthetic rubber is an elastomer or polymer which regains its size original shape
after being pulled or pressed. [Natural rubber is an elastomer too.]
Examples of synthetic rubber are neoprene and styrene-butadiene(SBR).
Neoprene
Synthetic rubber (Addition )
It is used to make
picture * rubber gloves and
* to insulate electric wires.
SBR is used to make
* tyres,
Styrene-butadiene or SBR picture
* soles of shoes and
* mechanical belts.
Synthetic Fibre



Nylon and terylene are synthetic fibres which undergo the condensation
polymerisation process.
These fibres resemble natural fibres but more resistant to stress and chemicals,
and more long-lasting.
In both cases, water is eliminated during the polymerisation process.
Nylon
Picture Nylon is used to make







umbrellas
curtains
socks
carpets
nylon string and rope
toothbrush
comb and so on
Terylene
Picture Terylene is used to make



fishing nets
clothes (quick-dry, non-iron)
cassette and video tapes
Issue in using synthetic polymer

Synthetic polymers have multiple uses in daily life because of the following
properties:
1.
2.
3.
4.
Light and strong
Cheap
Withstand corrosion and chemical reaction
Withstand action of water

Synthetic polymers are also used to replace natural polymers such as cotton, silk
and rubber.
However, synthetic polymers cause environmental pollution.

1. Most polymers are not biodegradable . Polymers cannot be decomposed
biologically or naturally by bacteria or fungi as in the case of other garbage. Thus,
the disposal of polymers has resulted in environmental pollution because they
remain in the environment forever.
2. Plastic containers and bottles strewn around become good breeding places for
mosquitoes which cause dengue fever, or malaria.
3. The open burning of plastics gives rise to poisonous and acidic gases like carbon
monoxide, hydrogen chloride and hydrogen cyanide. These are harmful to the
environment as they cause acid rain.
4. Burning of plastics can also produce carbon dioxide, too much of this gas in the
atmosphere leads to the `green house effect'.


The raw materials used to manufacture synthetic polymers are petroleum and its
by-products. Petroleum is a non-renewable source of fuel which is fast
diminishing from the earth's crust.
This problem can be overcome by the following ways:
1. Recycling polymers: Plastics can be decomposed by heating them without oxygen
at 700°C. This process is called pyrolysis. The products of this process are then
recycled into new products.
2. Inventing biodegradable polymers: Such polymers should be mixed with
substances that can be decomposed by bacteria (to become biodegradable) or light
(to become photodegradable) .
9.5Introduction
Uses of Glass and Ceramics



The raw materials used in the making of glass and ceramic materials are obtained
from the earth's crust. Silica or silicon(IV) dioxide, SiO2, form the most important
component of glass and ceramics.
In the SiO2 molecule, each silicon atom is held in a tetrahedral structure by four
oxygen atoms.
Each oxygen atom is held by two silicon atoms. This is repeated until a giant
three-dimensional molecule results.
Properties of glass and ceramic:

Both have the following properties:
1.
2.
3.
4.
5.
Hard and brittle
Do not conduct heat electricity
Inactive towards chemical reactions
Weak when pressure is applied
Can be cleaned easily
Glass


It is a mixture of two or more types of metallic silicates but the main component
is silicon(IV) dioxide.
Glass has the following properties:
1.
2.
3.
4.
5.
6.
Transparent and not porous
Inactive chemically
Can be cleaned easily
Good insulators of heat and electricity
Hard but brittle
Can withstand compression but not pressure

Due to the above reasons and the low cost involved to produce glass, it is used in
industry to make bottles, cooking utensils, plates and bowls, laboratory apparatus
(such as conical flask, beakers and test tubes), window panes, bulbs and others.
Different types of glass can be obtained depending on the composition of
substances in it.

Soda lime glass:



This is obtained when limestone (CaCO3) and sodium carbonate (Na2CO3) are
mixed with molten silica and cooled down.
It is also known as soft glass as it has a low melting point.
Most glass produced is soda lime glass. But it breaks easily, thus it is mainly used
to make kitchen utensils.
Lead glass:



This is formed when a mixture of lead(II) oxide, sodium oxide and silica is heated
together.
Lead glass of better quality contains a higher percentage of PbO.
Its refractive index and density being high, it has a glittering and attractive
surface, thus it is also called crystal glass.
Borosilicate glass:


Boron oxide (B2O3) and sodium carbonate is added to molten silica to obtain
borosilicate glass or pyrex..
The presence of B2O3 makes the glass able to withstand high temperatures and
chemical reaction. It does not break easily, thus it is used to make laboratory
apparatus and cooking utensils.
Fused silicate glass:



Sand (silica) is heated until it melts at 1700°C, and the viscous liquid is cooled
immediately. This produces a transparent solid with an uneven arrangement of
atoms, called fused silicate glass.
This glass cannot expand or contract easily when there are temperature changes.
But it cannot become misshapen because of its high melting point.
It is known as quartz glass.
Summary
Glass
Composition
Properties
Uses
• Low melting point
(700°C)
SiO2 – 70%
Glass containers, Glass panes,
• Mouldable into
Na20 – 15%
Soda lime,glass
shapes
Mirrors, Lamps and bulbs, Plates
CaO – 10%
• Cheap
and bowls Bottles
Others – 4%
• Breakable
• Can withstand high
heat
Lead glass
SiO2 – 70%
• High density and
Containers for drinks and fruit
(crystal)
Na20 – 20% refractive index
PbO – 10% • Glittering surface
• Soft
• Low melting point
(600°C)
SiO2 – 80%
Borosilicate
glass (Pyrex)
• Resistant to high
heat and chemical
reaction
Glass apparatus in laboratories
B203 – 13%
Na2O – 4%
Al203 – 2%
• Does not break
easily
• Allows infra-red
rays but not ultraviolet rays
• High melting point
(1700°C)
Fused silicate
glass
Decorative glass and lamps
Crystal glassware Lenses for
spectacles
SiO2 – 99%
6203 - 1%
• Expensive
• Allows ultraviolet
light to pass through
• Difficult to melt or
mould into shape
Cooking utensils
Scientific apparatus like lenses on
spectrometer
Optical lenses
Laboratory apparatus
[edit] Ceramics




Ceramic is a substance that is made from clay and hardened by heat in a furnace
maintained at a high temperature.
Clay is composed of aluminosilicate with sand and iron(III) oxide as impurities.
Iron(III) oxide, Fe203, gives a reddish colour to the clay.
Kaolin, or clay in its pure form, is white in colour. It consists of crystals of
hydrated aluminosilicate with the formula Al2Si2O7.2H2O or Al2O3.2SiO2.2H2O.
The different classes of ceramic include:
Group
Quartz – SiO2
Calcite – CaCO3
Mixture of CaSiO3 and aluminium silicate
Aluminium oxide – Al2O3
Silicon dioxide – SiO2
Magnesium oxide – MgO
Silicon nitride – Si3N4
Composition
Silicon carbide – SiC
Boron nitride – BN
Boron carbide – B4C3

The preparation of ceramic objects involves 3 stages:
1. A layer of water exists between the aluminosilicate crystals. This gives it a
plastic-like property when wet. Thus the clay is first wet to make it soft before it
is shaped.
2. The shaped object is then dried. At this stage, the product can still be reshaped by
adding more water.
3. The dried object is heated to a temperature of 1000°C in a furnace. The product of
this stage cannot be softened with water or reshaped.


The surface of ceramic object is usually coated with a layer of mineral or metallic
silicate and baked again in the furnace to produce a shining and impervious
ceramic object.
The properties of ceramics include the following:
1.
2.
3.
4.
5.
6.
Hard
Strong but brittle
Chemically inactive
Poor conductor of heat and electricity
High melting point – heat resistant
Cannot be compressed easily

The differences between the properties of ceramics, metals and non-metals are
given below.
Property
Metals
Hard but malleable and
ductile
Non-metals
Ceramic
Soft and
Hard but brittle
brittle
Density
High
Low
Average
Melting point
High
Low
Very high
Resistance to heat
High
Low
Very high
Heat and Electrical
conductivity
Good conductor
Good
insulator
Good insulator
Chemical reactions
Corrodes
Corrodes
Stable, does not
corrode
Hardness
[edit] New Uses of Glass and Ceramics

The latest use of glass is to make photochromic glass and conducting glass while
ceramics is used to produce superconductors and car engine blocks.
[edit] Photochromic glass



Photochromic glass is very sensitive to light. It darkens in the presence of bright
light and lightens when the amount of sunlight lessens.
The glass is produced by adding silver chloride (or silver bromide) and some
copper(II) chloride to normal glass.
Silver halides decompose to silver and its halogen when exposed to ultraviolet
rays. Thus we have:
It is the silver which makes the glass become dark.
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When there is a decrease in light, silver chloride is formed again:
Therefore the glass lightens.
[edit] Conducting glass
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Conducting glass is a type of glass which can conduct electricity. It is obtained by
coating a thin layer of a conducting material around the glass, usually indium
tin(IV) oxide or ITO.
Conducting glass can also be obtained by embedding thin gold strips into a piece
of glass. This is used to make the front windows of aeroplanes which tend to mist
at very high heights. By passing an electric current through this glass (containing
gold as conductors), the water of condensation will dry up.
Superconductors are electrical conductors which have almost zero (0) electrical
resistance. Therefore, this conductor minimises the loss of electrical energy
through heat.
Perovsite is a type of ceramic superconductor composed of itrium oxide, copper
oxide and barium oxide.
Superconductors are also used to make magnets which are light but thousands of
times stronger than the normal magnet.
Car Engine Block--When clay is heated with magnesium oxide, the ceramic that
is produced has a high resistance to heat. This material is used to build the engine
blocks in cars as they can withstand high temperatures.
9.6Introduction
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Composite materials are substances which contain 2 or more materials that
combine to produce new substances with different physical properties from the
original substances.
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They are used to make various substances in daily life because of the following
reasons:
1. Metals corrode and are ductile and malleable
2. Glass and ceramics break easily
3. Metals are good conductors but have high resistance, leading to loss of electrical
energy as heat
4. Plastics and glass can withstand heat to certain level only.
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Composite materials have been created to overcome these problems and to make
materials stronger, more long-lasting and light for specific purposes.
Some composite materials and their components are:
Uses of Composite Materials
[edit] Reinforced concrete
concrete (cement, sand, stones), steel
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Ordinary concrete is strong but heavy. Concrete pillars must be big to support the
weight. They take up space and cannot withstand stress for example from
earthquakes.
Steel pillars are too expensive and can rust.
Reinforced concrete, containing steel rods in the concrete pillars, can make them
stronger and able to support larger loads. It also does not rust.
[edit] Optical fibre
SiO2, Na2CO3, CaO
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This is a fine transparent glass tube that is made of molten glass. Glass cannot
conduct electricity or electronic data in the form of electrons. But optical fibre
allows light to be transmitted through the tube so that data is transmitted at a
faster rate.
In telecommunications, light has replaced electrons as the transmitter of signals.
This light transmits signals through optical fibre and the field is called
optoelectronics.
Optical fibre is also used in the medical field as
1. laser to do operation
2. endoscope to examine the internal organs of patients
[edit] Photochromic glass
glass, AgCl (or AgBr
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Glass is transparent and not sensitive towards light.
Photochromic glass contains AgCI or AgBr which causes the glass to darken in
sunlight and lighten in the absence of sunlight. (See 9.5.)
It is used to make photochromic lenses of spectacles and protects our eyes from
extreme sunlight.
[edit] Plastic reinforced with glass
fibreglass and polyster resin
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While plastic is light and hard, it is brittle. Glass is harder than plastic but breaks
easily. Thus fibre glass is obtained by adding a polyster resin to molten glass. It
cannot be compressed easily and is more tensile than the original materials.
Fibre glass is light, withstands corrosion, can be cast into different shapes, is
impervious to water, not very flammable, not brittle and stronger than even steel.
It is used to make racquets, construction panels, electrical appliances, pipes, and
water tanks.
[edit] Superconductor
Itrium oxide (Y203), BaCO3, CuO
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It is a substance with almost nil resistance. Thus it saves electricity.
Copper shows superconductor properties only at -270°C. Thus the
superconductor, a mixture of CuO, Y203, and BaO, results in a ceramic called
perovskite or YBCO. All the materials used to make this composite substance are
not electrical conductors in their original forms, but as a superconductor, it
conducts electricity without loss of energy. (See 9.5.)
[edit] Composite Materials to Fulfill Specific Needs
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Composite materials are needed in various fields, for example:
1. In the medical field: to replace organs in the form of plastic composite organs.
2. Car parts now use composite materials instead of iron and steel. This increases the
speed of the car (car is lighter) and saves on fuel consumption.
3. Stronger buildings are built by using reinforced concrete.
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