Topic 5.1-5.7 - Transition metals, alloys and corrosion

-high melting point -high density -They form coloured compounds -Are effective and useful as catalysts due to the catalytic activity of them and their compounds e.g. iron in the Haber Process

Corrosion, which is the destruction​ ​of​ ​materials​ ​by​ ​chemical​ ​reactions​ ​with​ ​substances​ ​in​ ​the environment

-Rusting​ ​can​ ​be​ ​prevented​ ​by​ ​excluding​ ​oxygen​ ​and​ ​water​ ​e.g.​ ​by: painting, coating​ ​with​ ​plastic, using​ ​oil​ ​or​ ​grease -Aluminium​ ​has​ ​an​ ​oxide​ ​coating​ ​that​ ​protects​ ​the​ ​metal​ ​from​ ​further​ ​corrosion​ ​– exclusion​ ​of​ ​oxygen​ ​and​ ​water

Electroplating​ ​acts​ ​as​ ​a​ ​barrier​ ​in​ ​order​ ​to​ ​exclude​ ​oxygen​ ​and​ ​water *It also​ ​improves​ ​appearance​ ​as​ ​you​ ​can​ ​electroplate​ ​a​ ​metal​ ​with​ ​an​ ​unreactive metal​ ​such​ ​as​ ​gold​ ​that​ ​is​ ​more​ ​attractive​ ​and​ ​will​ ​not​ ​corrode *It​ ​is​ ​done​ ​using​ ​the​ ​metal​ ​to​ ​be​ ​plated​ ​as​ ​the​ ​cathode​ ​and​ ​the​ ​metal​ ​you’re plating​ ​it​ ​with​ ​as​ ​the​ ​anode,​ ​then​ ​have​ ​a​ ​solution​ ​containing​ ​ions​ ​of​ ​the​ ​metal being​ ​used​ ​to​ ​do​ ​the​ ​plating

Sacrificial​ ​protection is ​where​ ​the​ ​metal​ ​you​ ​want​ ​to​ ​be​ ​protected​ ​from​ ​rusting​ ​is galvanised​ ​with​ ​a​ ​more​ ​reactive​ ​metal,​ ​which​ ​will​ ​rust​ ​first​ ​and​ ​prevent​ ​water and​ ​oxygen​ ​reaching​ ​the​ ​layer​ ​underneath

Steels​ ​are​ ​alloys​ ​since​ ​they​ ​contain​ ​mixtures​ ​of​ ​carbon​ ​and ​iron — though some​ ​steels​ ​contain​ ​other​ ​metals.​ ​Alloys​ ​can​ ​be​ ​designed​ ​to​ ​specific​ ​uses: *Low-carbon​ ​steels​ ​are​ ​easily​ ​shaped​ ​-​ ​used​ ​for​ ​sheeting​ ​(malleable) *High​ ​carbon​ ​steels​ ​are​ ​hard​ ​-​ ​used​ ​for​ ​cutting​ ​tools *Stainless​ ​steels​ ​(containing​ ​chromium​ ​and​ ​nickel)​ ​are​ ​resistant​ ​to corrosion​ ​-​ ​used​ ​for​ ​cutlery

In​ ​a​ ​pure​ ​metal,​ ​all​ ​the​ ​+​ ​metal​ ​ions​ ​are​ ​the​ ​same​ ​size​ ​and​ ​in​ ​a regular​ ​arrangement,​ ​allowing​ ​the​ ​layers​ ​to​ ​slide​ ​over​ ​each​ ​other​ ​relatively easily,​ ​making​ ​the​ ​metal​ ​soft​ ​and​ ​malleable.​ ​In​ ​an​ ​alloy,​ ​you​ ​have​ ​+​ ​ions​ ​of different​ ​metals,​ ​which​ ​have​ ​different​ ​sized​ ​ions.​ ​This​ ​disrupts​ ​the​ ​regular structure​ ​and​ ​prevents​ ​the​ ​ions​ ​being​ ​able​ ​to​ ​slide​ ​as​ ​easily,​ ​leaving​ ​a​ ​much harder,​ ​stronger​ ​metal.

It has a low density so is used for aircrafts

It is a good conductor so is used in electrical cables

It has good resistance to corrosion so is used in jewellery

(It is aluminium + magnesium) It has a low density so is used in cars and planes

(It is copper + zinc) It is hard and resistant to corrosion so is used in coins