Chapter 9 :Manufactured

SubstancesIn

Industry

Name : Nurul Nabila Binti Rosely Nor

I.C. number : 930821-14-5700

Class : Perdagangan Gigih ’09 & ‘10

Teacher’s name : Mrs Elizabeth A/P Koilpillay

Appreciation

Sulphuric Acid

Ammonia

Alloys

Synthetic Polymers

Glass and Ceramics

Composite Materials

I would like to give a big thanks to for giving me a help while I’m doing this folio. A special thanks also to my friends because they have

helped me.Lastly, I would like to say thank you to my

parents because they have helped me to finish this folio.

SULPHURIC ACID

USES OF SULPHURIC ACID

To manufacture fertilizers

1. Almost one-third of sulphuric acid is used to manufacture fertilizers.

2. examples : a) Ammonium sulphate is formed when sulphuric acid reacts

with ammonia

b) calcium hydrogen phosphate (superphosphate) is formed when sulphuric acid reacts with calcium phosphate.

To manufacture paint pigments

1. Neutralisation of sulphuric acid with barium hydroxide solution produces barium sulphate which is used as white pigment in paint.

To manufacture detergents

To manufacture synthetic fibres

1. Example : Rayon is produced by the sulphuric acid with cellulose threads soaked in alkaline solution.

To clean metals

1. Before electroplating, sulphuric acid is used for cleaning metals to remove the surface oxides.

H2 SO4 (aq) + 2NH3 (aq) (NH4)2 SO4 (aq)

H2 SO4 (aq) + Ba (OH)2 (aq) BaSO4 (S) + 2H2O (I)

2H2 SO4 (aq) + Ca (PO4)2 (S) Ca (H2PO4)2 (aq) + 2Ca SO4 (S)

To manufacture plastics

As an electrolyte in car batteries

To manufacture other chemicals

1. Examples : Pharmaceuticals, insecticides, tartaric acid and explosives.

MANUFACTURE OF SULPHURIC ACID IN INDUSTRY

CONTACT PROCESS

1. Contact process produces more than 90% of the world’s sulphuric acid

2. The raw materials used for the manufacture of sulphuric acid :

Sulphur

Air

Water

3. consists of three stages :

stage I – Production of sulphur dioxide

stage II – Conversion of sulphur dioxide to sulphur trioxide

stage III – Production of sulphuric acid

Stage 1 sulphur is burnt in air to produce sulphur dioxide

burning of metal sulphides also produce sulphur dioxide

the sulphur dioxide is then mixed with excess air

the mixture is dried and purified to remove impurities such as arsenic compounds

Stage 2 the mixture of sulphur dioxide and excess oxygen is pass through a converter

the sulphur dioxide is oxidized to sulphur trioxide

optimum conditions used are as follows

1. temperature : 450 C2. pressure : 1 atmosphere3. catalyst : Vanadium (V) oxide, V2O5

about 97% conversion occurs under these optimum conditions

S (s) + O2(s) SO2 (s)

2ZnS (s) + 3O2 (s) 2SO2 (s) + 2ZnO (s)2PbS (s) + 3O2 (s) 2SO2 (s) + 2PbO (s)

2SO2 (s) + O2 (s) 2SO3 (s)

Stage 3 the sulphur trioxide is first dissolved is concentrated sulphuric acid to form a product called oleum, H2S207

sulphur trioxide is not dissolved in water to form sulphuric acid

the oleum is then diluted with water to produce concentrated sulphuric acid of about 98%

SULPHUR DIOXIDE AND ENVIRONMENTAL POLLUTION

1. sulphur dioxide is acidic and poisonous. Inhaling sulphur dioxide causes coughing, chest pain and shortness of breath. It is the thought to be one of the causes of bronchitis and lung diseases.

2. acid rain occurs when there is sulphurous acid, sulphuric acid and nitric acid in the rain. These strong acid will cause the pH of the rain to fall between to fall 2.4 and 5.0

when sulphur dioxide dissolves in rainwater, sulphurous acid is formed

sulphur dioxide can react with oxygen and water to form sulphuric acid

3. Acid rain corrodes buildings, monuments and statues made from marble and sandstone. The calcium carbonate in the marble reacts with sulphuric acid from the rain to form calcium sulphate.

SO2 (g) + H2O (I) H2SO3 (aq)

2SO2 (s) + O2 (s) + 2H2O (I) 2H2SO4 (aq)

SO3 (s) + H2SO4 (aq) H2S2O7 (I)

H2S2O7 (I) + H2O (I) 2H2SO4 (aq)

4. acid rain corrodes metallic structures. The iron from the steel bridges reacts with sulphuric acid to form iron (II) sulphate.

WAYS TO CONTROL AND REDUCE THE EFFECTS OF ACID RAIN

I. Use low sulphur fuels to reduce emission of sulphur dioxide into the air.II. Add calcium oxide (lime), CaO, calcium hydroxide, Ca(OH)2 and powdered

limestone, CaCO3 into the acidic lake or river to neutralize the acids present.

CaO (s) + 2H (aq) Ca (aq) + H2O (I)Ca(OH)2 (s) + 2H (aq) Ca (aq) + 2H2O (I)

CaCO3 (s) + 2H (aq) Ca (aq) + CO2 (g) + H2O

STRUCTURE AND BASIC CHEMICAL PROPERTIES

The ammonia molecule has a trigonal pyramidal shape, as predicted by VSEPR theory.The nitrogen atom in the molecule has a lone electron pair, and ammonia acts as a base, a proton acceptor. This shape gives the molecule a dipole moment and makes it polar so that ammonia readily dissolves in water.The degree to which ammonia forms the ammonia ion increase upon lowering the pH of the solution.

CaCO3 (s) + H2SO4 (aq) CaSO4 (s) + CO2 (s) + H2O (I)

Fe (s) + H2SO4 (aq) FeSO4 (aq) + H2 (s)

NATURAL OCCURRENCE

Ammonia is found in small quantities in the atmosphere, being produced from the putrefaction of nitrogenous animal and vegetable matter.Ammonia and ammonium salts are found in small quantities in rainwater, whereas ammonium chloride and ammonium sulphate are found in volcanic districts.

HISTORY

The Romans called the ammonium chloride deposits they collected from near the Temple of Jupiter Amun in ancient Libya’sal ammoniacus’ (salt of Amun) because of proximity to the nearby temple.In the form of sal-ammoniac, ammonia was known to the Arabic alchemists as early as the 8th century, first mentioned by Geber (Jabir ibn Hayyan).Gaseous ammonia was first isolated by Joseph Priestly in 1774 and was termed by him alkaline air, however it was acquired by the alchemist Basil Valentine.

USES OF AMMONIA

To make fertilizers which provide plants nitrogen. These fertilizers are ammonium salts obtained from the neutralization of ammonia with different acids.

Example :

Ammonium Phosphate

The reaction of ammonia with phosphoric acid produces ammonium phosphates.

Ammonia is used as a raw material for the manufacture of nitric acid in the Ostwald process. This process involves three stages.

a) Ammonia is oxidized to nitrogen monoxide in the presence of platinum as the catalyst.

NH2 (aq) + H3PO4 (aq) NH4H2PO4 (aq)2NH3 (aq) + H3PO4 (aq) (NH4)2 HPO4 (aq)

b) nitrogen monoxide is further oxidised to nitrogen dioxide.

c) the mixture of nitrogen dioxide and air is dissolved in water to form nitric acid

liquid ammonia is used as a cooling agent in refrigerator because ammonia is highly compressible and has a high heat capacity.Ammonium salts is used as smelling salts to revive people who have fainted.

TO INVESTIGATE THE PROPERTIES OF AMMONIA

Material : 0.1 mol dm ammonia solution, 0.1 mol dm sodium hydroxide solution, ammonium chloride, calcium hydroxide, concentrated hydrochloric acid, soda-lime, distilled water, red litmus paper, pH paper.

Apparatus : test tubes, beaker, U-tube, Bunsen burner, glass rod, delivery tube, stoppers.

Procedure :

A. Preparation of ammonia gas

1) Some ammonium chloride is mixed with some calcium hydroxide.2) The apparatus is set up as shown in the diagram below.

Preparation of ammonia gas

3) the mixture is heated.

4NH3 (s) + 5O2 (s) 4NO (s) + 6H2O (I)

2NO (s) + O2 (s) 2NO2 (s)

4NO2 (s) + O2 (s) + 2H2O (I) 4HNO3 (aq)

4) The ammonia gas produced is collected in a few test tubes. The test tubes containing ammonia gas must be closed with stoppers.

B. Alkalinity of ammonia1) 5 cm of 0.1 mol dm ammonia solution and 5 cm of 0.1 mol dm sodium

hydroxide solution are poured into two separate test tubes.2) A piece of pH paper is dipped into the solution in each test tube.3) The pH values of both solutions are recorded.

C. colour, physical state, smell and solubility of ammonia

1) the colour and physical state of ammonia are observed.2) The stopper of a test tube containing ammonia gas is removed and the smell of

the gas is identified.3) A test tube containing ammonia gas is inverted into a beaker of water.4) All observations are recorded.

Testing the solubility of ammonia gas in water

D. Density of ammonia

1) A test tube containing ammonia gas is held upright and another test tube containing ammonia gas is held upside down.

2) The stoppers of the two test tubes are removed.3) After 20 seconds, a piece of moist red litmus paper is put at the mouth of each

test tube as shown in the figure below.

Testing the density of ammonia gas

4) the colour of the red litmus paper is recorded.

E. chemical property of ammonia

1) one end of a glass rod is dipped into concentrated hydrochloric acid2) the glass rod is then put on top of a test tube of ammonia gas.3) Any changes taking place is observed.

Observation :

Section observation InferenceA pH of ammonia solution is

10pH of sodium hydroxide solution is 14

o ammonia is a weak alkalio sodium hydroxide is a strong

alkali

B colourless gaspungent smellwater rushes up and fills up the whole test tube

o ammonia is a colourless gas with a pungent smell

o ammonia is very soluble in water

C moist red litmus paper on top of the upright test tube does not change colourmoist red litmus paper under the interved test tube turns blue

o ammonia gas has escaped from the upright test tube and thus is slightly less dense than air

D dense white fumes are formed

o ammonia reacts with hydrogen chloride gas to formed ammonium chloride

Discussion :

1) Ammonia is a weak alkali and has a pH of 10.2) Ammonia is a colourless gas with a pungent smell.3) Ammonia is very soluble in water, ionizes partically in water to form ammonium

ions and hydroxide ions.

4) ammonia is slightly less dense than air.5) Ammonia reacts with hydrogen chloride gas to form ammonium chloride.

Conclusion : ammonia is an alkaline, colourless gas with a pungent smell. It is very soluble in water and is less dense than air. It reacts with hydrogen chloride gas to form dense white fumes of ammonium chloride.

NH3 (s) + H2O (I) NH4 (aq) + OH (aq)

NH3 (s) + HCl (s) NH4Cl (s)

Haber process

used to produce ammonia from the nitrogen in the air.Developed by Fritz Haber and Carl Bosch in 1909 and patented in 1910.First used on an industrial scale by the Germans during World War 1.

Manufacture of ammonia in industry

1) the raw materials for the Haber process are hydrogen and nitrogen.2) Nitrogen and hydrogen are mixed according to the ratio 1 mole N2 : 3 moles H2

3) The mixture is compressed to 200 atom and heated to a temperature of about 450 C.

4) The mixture is then passed through layers of heated iron catalyst in a reactor. Ammonia is produced.

The reaction is reversible and the production of ammonia gives out heat. The high pressure and iron catalyst speed up the rate of reaction

5) the ammonia gas produced is liquefied and separated to get a better yield.6) The unreacted nitrogen and hydrogen are recycled and passed back into reactor

together with the new source of nitrogen and hydrogen.

N2 (s) + 3H2 (s) 2NH3 (s)

Ammonium Fertilisers

Contain ammonium ions. In the soil, the ammonium ions are converted to nitrate ions by bacteria.Examples of ammonium fertilizers :

I. Ammonium nitrate, NH4NO3

II. Ammonium sulphate, (NH4)2 SO4

The fertilizers that contain a high percentage of nitrogen are more effective than those fertilizers with a low percentage of nitrogen.Ammonium fertilizers can be prepared by reactions between ammonia solution and acids.

ALLOYS

PURE METALS

PHYSICAL PROPERTIES

High density High melting and boiling point Good conductors of heat and electricity Malleable Ductile Lustrous

1. the properties of a pure metal are reflected by its arrangement of atoms. It is made up of one type of atom, thus all atoms are of the same size.

2. in the solid state, the atoms in the pure metal are orderly arrangement and closely packed together. Thus, pure metals have high densities.

Atoms in a pure metal are orderly arranged and closely packed together.

3. the atoms in metals are orderly arranged in layers to form a three-dimensional crystal lattice. The forces of attraction between the very closely packed atoms are very strong. Thus, a large amount of energy is required to overcome these forces. As a result, pure metals have high melting and boiling points.

4. although the forces of attraction between the metal atoms are strong, they are not rigid. Therefore, when a force is applied, the layers of atoms can slide over one another. Thus, metals are ductile or can be stretched.

5. the arrangements of atoms in pure metals are not perfect. There are some empty spaces in between the atoms. When a metal is knocked or pressed, group of atoms may slide and then settle into new positions. This explains why metals are malleable or can be shaped.

6. Pure metals are weak and soft due to their ductility and malleability. Thus, pure metals have limited uses.

7. to improve the properties of a pure metal, it is made into an alloy.

ALLOYS

An alloy is a mixture of two or more elements with a certain fixed composition in which the major component is a metal. Most alloys are mixtures of metals. For example, bronze is an alloy of copper and tin. Both pure copper and tin are soft. When copper is alloyed with tin, bronze which is stronger and harder is produced. Some alloys may contain mixtures of a metals and a non-metal such as carbon. For example, steel is an alloy of iron and carbon. Iron is a soft metal. When some carbon is added to iron, steel which is stronger and harder is formed. Pure metals are normally soft and easily oxidized. This is the reason why monuments or statues are made of branze and not copper. Cutlery is made of stainless steel and not steel or iron. This is because stainless steel is shiny and does not rust. Alloys are stronger, harder, resistant to corrosion, have a better finish and lustrous. By changing the percentage of composition of the metals, the properties of the resulting alloy can be altered.

Factors of making alloy

a) To increase the strength and hardness of a pure metal

In the process of making alloys, atoms of other elements are added, usually in small amounts, into a molten pure metal.When the metal becomes solid again, the positions of some of atoms of other elements of different sizes.

The presence of the atoms of other elements disrupts the orderly arrangement of the pure metal. The layers of metal atoms are prevented from sliding over one another easily. This makes alloys strongers and harder than pure metals.

During the making of steel, carbon atom which are smaller than iron atoms are added into iron atoms. As a result, the uniformity of the arrangement of iron atoms is discrupted and it is more difficult for the layers of the iron atoms to slide over one another. This makes steel harder and stronger than pure iron.

b) To increase the resistance to corrosion of a pure metal

Unreactive metals such as gold and silver can be found in the free state. This is because they do not react with oxygen and water vapour in the air.

Most metals such as iron and copper corrode readily in the air. Alloying can prevent metals from corrosion. This is because alloying

helps to prevent the formation of oxide layer on the surface of the metal. for example, carbon, chromium and nickel are added to iron to make

stainless steel. Cutlery made from stainless steel does not corrode.

c) to improve the appearance of a pure metal

metals have lustrous surfaces. However the formation of dull metal oxide on the surface of a metal makes it quickly lose its shine.

Alloying helps to keep the metal surface shiny as its prevents the formation of the metal oxide.

Alloy Compositon Properties UsesBronze 90% copper

10% tinHard, strong, does not corrode easily

Medals, statues, monuments

Brass 70% copper30% zinc

Harder than copper Musical instruments,

kitchenware, door knobs

Cupro-nickel 75% copper25% nickel

Beautiful surface, shiny, hard

Coins

Steel 99% iron1% carbon

Hard, strong Buildings, bridges, body of cars

Stainless steel 74% iron8% carbon

18% chromium

Shiny, strong, does not rust

Cutlery, surgical instruments, sink

pipesDuralumin 93% aluminium

3% copper3% magnesium1% manganese

Light, strong Aircraft’s body, bullet trains

Pewter 96% tin3% copper

1% antimony

Shiny, strong, does not corrode

Art objects, souvenirs

Composition, properties and uses of alloy

SYNTHETIC POLYMERS

POLYMERS

The term ‘polymer’ originated from Greek words, ‘poly’ means ‘many’ and ‘mer’ means ‘parts’. Polymers are large long-chain molecules formed by joining together many identical repeating sub-units called monomers. Polymerization is a process by which the monomers are joined together into chain-like molecule called polymer. A polymer may consist of thousands of monomers.

M+M+M+M+M… -M-M-M-M-MOr

nM M where M = monomer, n = a big number

there are two types of polymers:

a) natural polymers obtained from living things such as plants animals.

RUBBER

Rubber is an elastic material obtained by “curdling” the milky sap (latex) of certain plants. Natives in Central America and Mexico used rubber before Columbus. In 1839, Charles Goodyear invented vulcanized rubber, a form of natural rubber modified by cross-linking (vulcanization). The monomer for natural rubber is isoprene or 2-methylbuta-1, 3-diene. Each isoprene unit has two double bongs. Isoprene molecules undergo addition polymerization to form poly (isoprene) or natural rubber.

b) synthetic polymers polymers made by man through chemical reactions. Monomers used for the manufacture of synthetic polymers are

usually obtained from the fractional distillation of petroleum. Used to make plastics, fibres, resins, and synthetic rubber. Prepared through addition polymerization and condensation

polymerisation.

Addition polymerization Condensation polymerization Involves monomers with double

bonds between the carbon atoms. Examples : ethane and styrene.

Involves the joining up of monomers with the formation of other smaller and simple molecules such as water

Examples : nylon and terylene.

PLASTICS

The first man-made plastic was invented by Alexander Parkes in 1862. he called this plastic Parkesine. The development of plastics has come from the use of natural plastic materials to the use of chemically modified natural materials and finally to completely synthetic molecules. The raw materials used to make plastics are obtained from the products of cracking of petroleum fractions. They are normally alkene molecules and are made into plastics through addition polymerization. Plastics are the largest group of synthetic polymers. It has low density, strong and inert to chemical too.Here are some commonly used plastics :

Polyethylene : shopping bags Polyvinyl chloride : pipes Polystyrene : packing materials Perspex : lenses

SYNTHETIC FIBRES

Synthetic fibres are long-chain polymers which are not easily stretched and have high strength. Polyamides and polyesters are two group of synthetic polymers used as fibres for making textile.

NILON

The real star of the plastics industry in the 1930s was “polyamide” (PA), far better known by its trade name nylon. Nylon was the first purely synthetic fibre, introduced by DuPont Corp at the 1939 World’s fair in New York City.

Nylon is used to make toothbrushes, ropes, fishing lines, papachutes, carpets, textile, threads, and electrical insulators.

TERYLENE

Terylene is an example of polyester polymers and are diol molecules and diacid molecules.

Terylene is chemically inert, elastic and can be coloured and easily made into fibres.

It is suitable for making textile, stocking, parachutes and fishing nets.

SYNTHETIC RUBBERS

A polymer that was critical in World War II was “synthetic rubber”, which was produced n a variety of forms. It is not plastics and are elastic materials. These synthetic polymers are also called elastomers. Produced by addition polymerization, neoprene and styrene-butadiene are examples of synthetics rubbers.

SYNTHETIC POLYMERS IN DAILY LIFE

About 57% of the total production of polymers are used in packaging and building industries. The uses of synthetic polymer are determined by its structure and properties. Synthetic polymers are very stable. Unlike metals, wood or paper, they do not rust, rot or decay. They are very useful but they also difficult to dispose of as they are not easily biodegradable. Disposal of synthetic polymers has caused environmental pollution problems.

Ways to solve the problems caused by the use of synthetic polymers

Reuse Recycle Use biodegradable synthetic polymers Dispose of unwanted synthetic polymers in a proper manner

GLASS AND CERAMICS

Glass

Glass is normally referred to a transparent, shiny substance that breaks rather easily. Evidence has shown that glass has been used for more than 3000 years ago.

1. silica or silicon dioxide, SiO2 is the major component of glass. It can be found in sand.

2. glass can be made by heating a mixture of silicon dioxide and metal carbonates to a temperature above 1500 C.

when sodium carbonate, Na2CO3 are heated to a high temperature, they decompose to form metal oxides.

the metal oxides then combine with silicon dioxide to form the respective metal silicates.

the overall reaction is as follows.

glass is a mixture of metal silicates.

3. In silicon dioxide, each silicon atom forms covalent bonds with four adjacent oxygen atoms in a tetragonal shape. Each oxygen atom is bonded to two silicon atoms to form a macromolecule.

2SiO2 (s) + Na2CO3 (s) + CaCO3 (s) NaSiO3 (s) + CaSiO3 (s) + 2CO2 (s)

Na2CO3 (s) Na2O (s) + CO2 (s)CaCO3 (s) CaO (s) + CO2 (s)

SiO2 (s) + Na2O (s) Na2SiO3 (s)Sio2 (s) + CaO CaSiO3 (s)

4. in glass, the SiO3 tetrahedras bond together by sharing oxygen atoms to build up a giant non-regular 3-D structure containing the Si-O-Si linkages. Sodium ions and calcium ions balance the negatively-charged silicate ions.

5. the physical properties of glass depend on percentage of the various silicates present. Generally, all types of glass have the following common properties. Transparent Hard but brittle Impermeable to liquid Heat insulator Electrical insulator Chemically inert

Types and uses of glasses

Type of glass Composition Properties UsesFused glass Silicon

dioxide High melting

point High temperature

and chemically durability

Laboratory glassware

Lenses Optical fibres

Soda-lime glass

Silicon dioxide

Sodium oxide

Calcium oxide

Low melting point

Easy to mould and shape

Transparent to visible light

Containers Flat glass Windowpanes Mirrors Light bulbs

Borosilicate glass

Silicon dioxide

Boron oxide

Sodium oxide

Calcium oxide

Resistant to chemicals

Resistant to thermal shock

Cookware Laboratory

glassware Electrical tubes

Lead crystal glass

Silicon dioxide

Lead(II) oxide

Sodium oxide

High density High refractive

index Soft and easy to

melt

Tableware Art objects Crystals

Ceramic

Pieces of broken ceramics from more than 6000 years ago have been found by archaelogists. Pottery is the oldest form of ceramic products.

1. ceramics are made from clay such as kaolin. Kaolin is rich in kaolinite (hydrated aluminosilicate, Al2O3.2SiO2.2H2O).

2. when the clay is heated to a very high temperature, it undergoes a series of chemical reactions and is hardened permanently to form ceramics.

3. these chemical changes are not reversible and the ceramic cannot be melted and remoulded.

4. bricks, tiles, mugs, and clay pots are some examples of ceramics.

Properties and uses of ceramics

Property Uses ExamplesHard and strong Building materials Tiles, bricks, roofsattractive, easily moulded and glazed

Decorative pieces and household items

Vases, porcelain ware, sinks, bathtubs

chemically inert and non-corrosive

Kitchenware Cooking pots, plates, bowl

Very high melting point and good insulator of heat

Insulation Lining of furnace, engine parts

Electrical insulators Insulating parts in electrical appliances

Spark plugs, insulators in oven and electric cables

Inert and non-compressible Medical and dental apparatus

Artificial teeth and bones

Comparing properties of glass and ceramics

Common properties of glass and ceramics

hard and do not bend strong under compression brittle good heat and electrical insulators inert to chemicals do not corrode

differences between glass and ceramics

glass can be heated until molten repeatedly but not ceramics glass is usually transparent whereas ceramics are not glass has a lower melting point than ceramics

special glass and ceramics

glass optical fibres

Glass optical fibre is a pure silica glass thread that conducts light. This fibre can transmit messages modulated onto ight waves. Using a glass optical fibre, information such as telephone and tv signals as well as digital data can be transmitted over long distances without distort and loss of signal. Optical fibre is particularly popular in local area networks (LAN), control board displays and medical instruments. Fibre optic cables are much thinner and lighter than the traditional metal cables. They can carry more data and less susceptible to interference than metal cables.

Photochromic glass

Photochromic glass is made when a glass is embedded with certain photosensitive chemicals that change colour when exposed to light. It darkens when exposed to ultraviolet rays and clears up when the rays are removed. It is also used for windows, sunglasses and instrument controls.

Glass-ceramics

Glass-ceramics are strong materials made by heating glass to rearrange some of its atoms into regular patterns. It have better mechanical strength and are better electrical insulators compared to normal glass. They can withstand high temperatures, sudden changes in temperature and chemical attacks better than the normal glass. Glass-ceramics have been used in cookware, rockets, tiles and engine blocks.

COMPOSITE MATERIALS

Made by combining two or more materials.

Examples :

reinforced concrete- a mixture of concrete and steel rods superconductor- a combination of metals and metals oxides fibre glass- glass fibres embedded in plastic resins photochromic glass- a mixture of glass and photosensitive or lightsensitive

substances

reinforced concrete

concrete is a composite material which consists of a mixture of stones, chips and sand bound together by cement. It is strong but brittle and weak in tensile strength. When concrete is reinforced with steel wire netting or steel rods, the resulting combination is a very tough material with high tensile strength.

Superconductors

Superconductors are capable of conducting electricity without any electrical resistance when they are cooled to an extremely low temperature. Most of superconductors are alloys of metal compounds or ceramics of metal oxides. It is used in :

magnetic energy-storage systems generators transformers computer parts

fiberglass

fiberglass is produced when glass fibres are embedded in plastic resins to produce glass fibre reinforced plastics. Fibreglass has high tensile strength, can be easily coloured, moulded and shaped. It is used in the making of water storage tanks, badminton rackets, helmets, small boats skis and car bodies.