chapter 8 form 4 scince

7/29/2019 chapter 8 form 4 scince

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Chapter 8: Chemicals in Industry

8.1 properties of alloys and their uses in industry

8.1.1 Alloy

1. An alloy is a solid mixture of at least one metallic element melting in it.

2. Examples: steel, pewter, bronze, brass, duralumin and etc.3. The mixture of metals in alloys follows a specific percentage rate.

4. Alloying produces a new substance which has different properties from the original metal.

5. Alloying is carried out to improve the weakness and structure of pure metals. Pure metals are

a) Soft and weak

b) Rust easily, make it less shinny and dull: metal + oxide = metal oxide

c) Less durable

d) Not suitable for various uses

6. Alloys are better than pure metals because:

a. More harder and stronger

b. More resistant to corrosion

c. Better appearance

7. Pure metals are weaker than alloy because, in pure metals atoms are arranged neatly in rows.

The rows can slide over each other easily when force is applied. This makes the pure metal to

be:

a) Ductile

b) Malleable

c) Easily shaped

8. When another metal is added, its atoms stop the row from sliding over each other. This is

because the added metal has atoms of a different size.


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9. Comparison between a pure metal and an alloy

Pure metal Alloy

Atoms are arranged orderly and closely

together

Other atoms are randomly scattered and are

filled between pure metal atoms.

The layers of atoms slide easily over one

another

There is no layered structure. The pure metal

atoms are unable to move because the

addition of foreign atoms hols them in place.

Ductile and malleable. Harder, non-ductile and non-malleable

10. Composition, properties and uses of alloys in daily life.

Type of alloy Composition Properties UsesBrass 70% copper

30% zincHard and malleableResistant to corrosion

Making kitchenappliances andornaments

Bronze 88% copper

12% tin

Hard and malleable

Can withstand corrosionbetter than copperShinny

Making decorative

ornaments and trophies

Duralumin 95% aluminium5% copper

Light and strongResists corrosion

Making aircraft bodies,bicycle frames andmodern jets

Stainless steel 74% iron18% chromium8% nickel

Same as carbon steel butits appearance is shinnyCan withstand corrosionbetter than carbon steel

Cutlery like forks, spoonsand surgical knivesBuilding construction,bodies of cars, pipes

Pewter 96% tin3% copper

1% antimony

Soft, shiny and malleable Making decorativeornaments and drinking

mugsHigh carbonsteel

99% iron1% carbon

Strong, hardHigh wear resistantWithstand great pressure

Making of cutting tools,hammers and chisels

Cupronickel 75% copper25% nickel

Attractive, silveryappearanceHard and tough

Making of silver coins

Magnalium 70% aluminium30% zinc

Light hard and strong Aircraft body frames andrims of racing car types

8.1.2 The importance of Alloys in Industry

1. Alloys are widely used in industries because they have more desirable properties than pure

metals.

2. One of the main contributions of alloy is in the form of superconductor alloy.

3. Superconductor alloy:

a. Are electrical conductors which do not have electrical resistant to the flow of electricity in

certain temperature.

b. Allow high current to flow through them without producing heat as compared to normal

conductors.

c. Also shows diamagnetic properties which are repelled by magnets.


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d. Superconductor alloys are used to make very light, small and strong magnets in:

i. The medical field- The magnetic resonance imaging (MRI) machine uses

superconductor alloy to produce a strong magnetic field which helps medical

specialist to do diagnosis more accurately before operation or other treatment.

Superconductor alloys such as niobium-titanium and niobium-tin are used in

construction of MRI apparatus.

ii. Bullet trains- The train uses the help of a magnet to move as though it if floating.iii. The production of electrical energy- A magnetic superconductor alloy in a nuclear

reactor can produce more electrical energy

8.2 Production and Uses of Ammonia in Industry

1. Ammonia is a:

a. Colourless gas with pungent smell

b. Very soluble in water

c. Produces alkali (ammonium hydroxide) in water

2. In industry, ammonia is produced by Haber process

Iron catalyst

Nitrogen + Hydrogen Ammonia

450 C 550 C, 200 atm

3. Ammonia and its compounds are used for:

a. Making nitric acid in large scale through Ostwald process. Ammonia as the raw material.

b. Making ammonium fertilisers which can supply nitrogen to plants

Ammonia + sulphuric acid ammonium sulphate + water

Ammonia + nitric acid ammonium nitrate + water

Ammonia + carbon oxide urea + water

c. As a cooling agent as ammonia gas is easily compressed and has a high heat capacity

d. Making chemical substances such as in dyes, synthetic nylon fibres, pharmaceutics and

refrigerants

e. As a cleaning agent - Ammonia solution reacts with vegetable oil or hydrocarbon to

produce cleaning agents

f. Preventing the coagulations of rubber latex

g. Making explosive substances such as trinitrotoluene (TNT)


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8.3 Effects of Industrial Waste Disposal on the Environment

1. Without proper disposal, industrial waste can cause environment pollution.

2. Poisonous and harmful industrial wastes in all forms are released from factories and

laboratories into the environment, causing pollution.

3. The two main industrial activities which cause the pollution are:

a) The burning of fossil fuels

b) The direct disposal of industrial wastes from the factories

Sources of pollution Pollutants Effects on the environmentBurning of fossilfuels in electricalpower plants andother industrialfacilities

Air pollutants suchas sulphur oxides,nitrogen oxides,hydrocarbons,carbon oxides andsoot

a) Irritate the respiratory system, leading toasthma or chronic bronchitis

b) Carbon monoxide reduces the ability of theblood to transport oxygen, causing headacheand fatigue, mental impairment or evendeath.

c) A high-level of carbon dioxide and othergreenhouse gases in the atmosphere cancause global warming

d) When acidic gases such as sulphur andnitrogen oxides dissolve in rain water, causesacid rain. Acid rain can damage the forestand aquatic ecosystems

Chemical industry Toxic waste such asacids, alkali andheavy metals, oiland untreated waste

a) Heavy metals such as mercury can damagethe brain and kidneys. It also can cause birthdefects.

b) Pollute the land and water, making it

Uses of

Ammoni

a

Nictric acid

Fertilisers

Nylon

production

ExplosivesRefrigerants

Pharmaceutica

ls

Household

cleaners


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matters undrinkablec) Aquatic animals and plants are effected by

dissolved oxygen level in waterd) Vapours of benzene and hydrocarbons can

move upwards and are inhaled by humanscan cause cancer in ling term

Mining and

processing ofradioactive minerals,nuclear power plant,nuclear weaponindustry, medicaland scientificresearch facilities

Radioactive wastes Exposure to radiation from radioactive wastes

causes serious health problems in living things.These include various types of cancers, mutations,sterility and birth defects

Agricultural industry Excessive artificialfertilisers andpesticides andorganic waste

a) Long term exposure to pesticides can causea variety of cancers and birth defects

b) Excessive fertilisers washed to the lakescause eutrophication

c) Open dumps of organic wastes are breeding

grounds for disease vectors such as rats andflies.d) Methane gas is released when this organic

waste is decomposed by microorganismse) Aquatic animals and plants are effected by

dissolved oxygen level in water

4. The control of industrial waste can be

carried out through the following ways:

a) Law enforcement

b) Education

c) Recycling waste

d) The use of technology in treating

industrial waste

e) Using an electrostatic precipitator

f) Plasma torch

g) Modern landfills

h) Switch from fossil fuels to solar

energy

i) Using a scrubber

j) Direct burning

k) Disposal drumsl) Biogas technology

chapter 8 form 4 scince

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