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Physical

propertiesof metals

Malleable

(can be hammered into shapes

without breaking)Ductile

(can be drawn into wires)

Conductor of heat and electricity

(Recall: Metallic bonding)

High melting points and boiling

points (except Gr I metals)

Subtopics/Main Ideas

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Experiment to show that metalsconduct electricity

4

lights

Metal

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Draw the circuit diagram

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How do metals conductelectricity?

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Watch the Flash Animation onmetallic bonding

Metallic bondingis the forceof attraction between_______________ ions andthe ____________ electrons.delocalised

positive metal

When a potential difference is applied across the metal, the electronsmove towards the direction of the positive terminal.

Positive ions

delocalisedelectrons

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AlloysSubtopics/Main Ideas

Mixture of metals and otherelements

Bronze = copper + tin

Brass = copper + zinc

Stainless steel = iron + carbon +chromium + nickel

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Structure ofPure Metals

Subtopics/Main Ideas

Atoms : same size and regulararrangement

They can slide over one another easily.

This makes pure metals soft.

This also explains why metals aremalleable and ductile.

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AlloysSubtopics/Main Ideas

Atoms : different sizes and irregulararrangement

They cannot slide easily over oneanother.

Hence, alloys are stronger and lessmalleable.

This explains why alloys are

preferred to pure metals.

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Uses of

Steel Alloys

Steel: Mixture of iron and carbon

Mild Steel

Uses: Car bodies and machineries

Reason: Hard, strong and

malleable

High Carbon Steel

Uses: Cutting and boring tools

Reason: Strong but brittle

(* as the amount of carbon added

increases, the strength of the alloy

increases but the alloy will be

more brittle as the layer of atomsare unable to slide easil

Subtopics/Main Ideas

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Test your understanding

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Properties of Metals

Cooking pots are sometimes made of copper.

Explain why copper is used for this purpose.

Copper is a good conductor of heat

And it will not corrode.

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Although aluminium is a reactive metal, whyis it often used in.

Aluminium has a protectivelayer of aluminium oxide.

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Importance of steel in everyday lives

Steel (1)

What is the base material for makingsteel?

What impurities are needed to beremoved?

Why is oxygen blown into meltedsteel?

What is the final step in steelmaking?

Steel (2)

IRON

CARBON

TO REMOVE IMPURITIES

OTHER ELEMENTS AREADDED TO ADJUST THECOMPOSITION OF STEEL

http://steel%20making%20-%20%282%29.flv/http://introduction%20to%20steelmaking.flv%20-%20%281%29.asf/