Uses of common metals
The importance of metals
Which metals are used most
Metal Tonnes per year
FeAlCuAu
400 000 000
15 000 000
8 000 000
2 000
Quantities of some common metals used
How to choose a metal
Common physical properties
1.Metals conduct electricity
2.Metals conduct heat.
3.Metals are shiny (though a few metals turn dull after exposure to air)4.Metals are malleable.5Metals are ductile.
Differences in physical Properties
1. Hardness and strength
2. Density
3. Melting point
Resistance to corrosion
Price of metals
Two important factors are
The abundance of the metal in the earth.
The cost of extraction.
Metal Uses Reasons for choice of metal
Al Cooking foil,drink cans
Window frames
Overhead electricity
Low density,strong,very
Fe Ship building and bridge Strong,cheap
Sn Tin plate,as found in food cans
Non-toxic,resists corrosion
Cu Wires
Water pipes
Ductile,good conductor of electricity,strong,malleable,resists corrosion
Au Jewellery,decoration
protective
Shiny and attractive,the most malleable metal
Good reflector of heat and light
Pb batteries Soft,dense and heavy,resists corrosion
Ti Supersonic aircraft Light,but very strong
Corrosion resistant
Cost perTonne($)
10400
1300
42000
71 million
11200
3900
(a) In the past, copper was used to make these cables.Give at least Two reasons for the choice of copper. (b) Aluminium is used today.Give some reasons for the change.
(c) Sodium is an excellent conductor of electricity and is light (density =0.97g/cm³).Why is it not used to make overhead electricity cables?
(d) The cables have a steel wire in the centre.Give a reason.
The figure shows overheadelectricity cables
CLASS PRACTISE (1)
good electrical conductor ,ductile.resistant to corrosion,not too expensive
Aluminum.Cheaper,much lighter (therefore pylons can be made more Cheaply to support the lighter weight).It is also a good electrical conductorAnd resistant to corrosion
Too soft,not very ductile,reacts with air and water
To provide more strength to the cable.
The handlebars of a bicycle are made of iron covered with a thin
layer of chromium(Cr)
What property of chromium is used?
Why are the handlebars not solid chromium?
Shiny appearance
Expensive
Imagine gold is cheap and iron is expensive . List:
(a) Some advantages of making a car from gold and not iron
Shiny,attractive, malleable, resistant to corrosion
(b) Some disadvantages.
Too heavy
Metal Malleability and ductility
Density Heat conductivity
Electrical conductivity
Corrosion resistance
Price
A Fair Medium Fair Fair fair Cheap
B Good Low Good Good Very good
Medium
C Very good
High Good Good Very good
Expensive
D Very good
medium good good Fair medium
(2)The table below gives the relative properties and prices of four metals
Decide which of the four metals,A to D,you would choose to make the following,objects.Give reasons for your choice.(a) A saucepan
(c) A bridge(d) A window frame
(b) Electrical wires
B-light,corrosion resistant,not too expensiveB-ductile,light,good electrical conductor,corrosion resistant,not too expensive
A-cheap,fair corrosion resistant (can be painted)D-malleable,fair corrosion resistant,not too expensive
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