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STUDYSMART CHEMISTRY FORM 4

CHAPTER 9 : MANUFACTURED SUBSTANCES IN INDUSTRY

9.1 Understanding the manufacture of sulphuric acid 9.2 Synthesising the manufacture of ammonia and its salts 9.3 Understanding Alloys 9.4 Evaluating uses of synthetic polymers 9.5 Applying uses of glass and ceramics 9.6 Evaluating uses of composite materials 9.1 UNDERSTANDING THE MANUFACTURE OF SULPHURIC ACID

Sulphuric acid, does not occur naturally. It has to be manufactured.

Sulphuric acid is manufactured in industry through contact process. The raw materials used are sulphur, air and water.

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9.2 SYNTHESISING THE MANUFACTURE OF AMMONIA AND ITS SALTS

Ammonia is manufactured in industry through Haber process.

This process combines nitrogen gas from the air with hydrogen gas derived mainly from natural gas to form Ammonia, NH3.

Preparation of ammonium fertilizer - Ammonium fertilizers contain ammonium ions. In the soil, the ammonium ions are oxidised to nitrate ions. - Example of ammonium fertilisers:

a) Ammonium sulphate (NH4)2SO4 b) Ammonium nitrate NH4NO3 c) Ammonium phosphate (NH4)3PO4

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9.3 UNDERSTANDING ALLOYS

Is mixture of two or more elements with a certain fixed composition in which the major component is metal.

Pure metals are make-up of the same type and same size of atoms.

The orderly arrangements of atoms make the metal ductile and malleable.

Orderly arrangement of atoms in metal enables the layer of atoms to slide on one another when force is applied

FORCE

Most pure metals are weak and soft.

The properties of pure metal can be improved by making them into alloys.

Alloys are stronger, harder, and resistant to corrosion, have a better furnish and luster

Examples of alloys are bronze, brass, steel, stainless steel, duralumin, and pewter

ALLOY COMPOSITION PROPERTIES USES

Bronze 90% copper and 10% tin Hard and strong Does not corrode Has shiny surface

Brass 70% copper and 30% zinc Harder than copper

Steel 99% iron and 1% carbon Hard and strong

Stainless steel

74% iron, 8% carbon and 18% chromium

Shiny Strong Does not rust

Duralumin 93% aluminium, 3% copper, 3% magnesium, 1% manganese

Light Strong

Pewter 96% tin, 3% copper, 1% antimony

Lustre Shiny Strong

Arrangement of atom in pure Metal: Closely packed & in an orderly manner

Layers of atoms slide over each other.

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Why make alloy a) To improve the appearance of the pure metal b) to increase the strength and hardness of the pure metal c) to increase the resistance to corrosion of the pure metal

The arrangement of atoms in alloy

The presences of atoms of other metals that are of different size disturb the orderly arrangement of atoms in the metal. This decrease the layer of atoms from sliding.

Thus alloy is stronger and harder than its pure metal.

9.4 EVALUATING USES OF SYNTHETIC POLYMERS

Polymer is made from large molecules make up of many identical repeating sub-units called monomers which are joined together by covalent bonds.

Polymerization : a process to join the monomer into chains by repeated linking.

2 types of polymer : a) naturally occurring polymers Examples : starch, cellulose, wool, protein, silk, natural rubber b) Synthetic polymers : man-made polymer. Examples : polythene, polyvinyl chloride (PVC), polypropene, perspex, nylon and terylene

Importance of Polymers are :

SYNTHETIC POLYMER

MONOMER USES

Polythene Ethene Plastic bags, shopping bags, plastic container, and insulation for electrical wiring

Polypropene Propene Piping, bottle crates, carpet, car batteries, and rope

PVC Chloroethene Artificial leather, water pipes, and records

Perspex Methylmethacrylate Safety glass, reflectors, traffic signs, and lens

Terylene Hexane,1-6-diol Benzene-1,4-dicarboxylic acid

Clothing, sails and ropes

Nylon Hexane-1.6-diamine Hexane-1,6- dioic acid

Ropes, clothing, and carpets

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9.5 APPLYING USES OF GLASS AND CERAMICS

Glass : made from sand

The major component: silica, SiO2.

There are so many types of glass; fused glass is the simplest one which is mainly silica, SiO2.

Fused glass : Highly resistant glass. It can be heated to an extremely high temperature and then can be plunged into icy, cold water without cracking.

Its expensive but still widely used because of its : 1. Great purity 2. Optical transparency 3. High temperature 4. Chemical durability 5. Resistance to thermal shock.

It is used as : 1. Laboratory glassware 2. Lenses 3. Telescope mirrors 4. Optical fibers. Ex : Starch, cellulose, wool, protein, silk and natural rubber.

The most common glass : Soda lime glass - Made by heating sand with limestone/ sodium carbonate. - Can be melted at a relatively low temperature - Easy to be shaped and has a good chemical durability. - High thermal expansion coefficient. - Expands a lot when it is heated and contracts a lot too when it is cooled. - Do not withstand heat.

Used to make : flat glass, electrical bulbs, mirrors and glass containers.

Soda lime glass + Boron oxide, B2O3 Borosilicate glass - Has a lower thermal expansion coefficient - 3 times as heat resistant as soda-lime glass - More resistant to chemical attacks because it contains less alkali. - Good to use in cookware, laboratory glassware and automobile headlight. - Used in glass pipelines and applications which require superior resistance to thermal shock

and greater chemical durability.

Ceramic are made from clay. Ex : Kaolin ( Aluminiumsilicate, Al2O3.2SiO2.2H2O )

When the clay is heated to a very high temperature, they undergo a series of chemical reactions and are hardened permanently to form ceramic. Ex : clay pots, bricks, tiles and mugs.

Ceramics are very hard, brittle, chemically inert, do not corrode, high melting point and are good insulators of electricity and heat.

Suitable for making abrasive, construction material, tableware, insulators in electrical equipment and refractories.

Comparing properties of glass and ceramics Similarities : Hard, Brittle, strong under compression, do not corrode, good electrical insulator, good heat insulator, resistant to chemical attacks

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Difference :

Glass Criteria Ceramic

Highly transparent Optical transparency Opaque

Can be melted and remoulded Moulding Cannot be melted and remoulded

Lower melting point Melting point Very high melting point

9.6 EVALUATING USES OF COMPOSITE MATERIALS

Structural material that is formed by combining two or more different substances such as metal, alloys, glass, ceramic and polymers. These materials are created for specific application.

The material formed has properties that are better than the original components. Types of composite materials Reinforced Concrete

Concrete: Consists a mixture of stones, chips and sand bound together by cement. It is strong but brittle and weak in tension.

Steel : Strong in tension.

Concrete reinforced with steel wires, steel bars or any polymers fibres, the resulting combination is a very tough material with more tensile strength.

The composites are good for the construction of large structures like high-rise building, bridges and oil platforms.

It is also cheap and can be moulded into any shape. Superconductors

Capable of conducting electricity without any electrical resistance when they are cooled to extremely low temperature.

They are used in the bullet trains in Japan, magnetic energy-storage systems, generators, transformers and computer parts.

Fibre optic

Fibre optic cable consists of a bundle of glass or plastic threads that are surrounded by a glass cladding.

They are used to replace copper wire in long distance telephone lines, in mobile phone, video camera and to link computer within local area network.

Fibre optic is good to use because they have law material costs, high transmission capacity, chemical stability and less susceptible to interference.

Fibre Glass

Formed when glass fibres are used to reinforce plastic.

Properties : High tensile strength, can be easily coloured, low in density easily moulded and shaped and can be made into thin layers.

Used to make household products like water storage tanks, badminton rackets, small boats, skis and helmets.

Photochromic Glass

Produced by embedding photochromic substances like silver chloride, AgCl crystals in glass or transparent polymers.

Used for making optical lenses, car windshields, smart energy efficient windows in buildings, information display panels, lense in cameras, optical switches and light intensity meters.