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