15 Metals

METALSMETALS

► Properties of MetalsProperties of Metals► Extraction of MetalsExtraction of Metals

► Uses of MetalsUses of Metals

Metals: What are Metals?Metals: What are Metals?

► It’s rather hard to imagine a world without It’s rather hard to imagine a world without metals. metals.

► Look around you – the chairs you’re sitting Look around you – the chairs you’re sitting on have metal frames; the cutlery you use on have metal frames; the cutlery you use during recess is made of steel (an alloy of during recess is made of steel (an alloy of iron); the wires in your MP3 player are made iron); the wires in your MP3 player are made of copper, another metalof copper, another metal

► What exactly are metals and what makes What exactly are metals and what makes them suitable for the uses which we put them suitable for the uses which we put them to?them to?

Metals: Physical PropertiesMetals: Physical Properties► Metals are Metals are malleablemalleable

They can be bent into They can be bent into many shapes.many shapes.

► Metals are Metals are ductileductile They can be drawn in They can be drawn in

thin wires.thin wires.

► Metals are Metals are good good conductors of conductors of electricityelectricity They are made into wires They are made into wires

and various electrical and various electrical goods like lamps, etc.goods like lamps, etc.

Metals: Physical PropertiesMetals: Physical Properties► Metals are Metals are good good

conductors of heatconductors of heat They are made into heating They are made into heating

coils and cooking coils and cooking instruments like woks and instruments like woks and pans.pans.

► Metals have Metals have high melting high melting and boiling pointsand boiling points They are made into They are made into

filaments of lamps which can filaments of lamps which can glow white hot and still not glow white hot and still not melt i.e. tungstenmelt i.e. tungsten

Exception: Mercury – The Exception: Mercury – The onlyonly liquid metal liquid metal

Metals: What is an Alloy?Metals: What is an Alloy?

► An An alloyalloy is a is a mixture of 2 or more mixture of 2 or more metallic elements metallic elements e.g. brass, pewtere.g. brass, pewter

► Some even contain Some even contain non-metallic non-metallic elements e.g. steelelements e.g. steel

► Alloys are stronger Alloys are stronger and harder than and harder than pure metals. Why?pure metals. Why?


►Pure metals are too soft because the Pure metals are too soft because the layers of atoms can slide over each layers of atoms can slide over each other easilyother easily


► In an alloy, atoms of different metals In an alloy, atoms of different metals are of different sizes.are of different sizes.

►This disrupts the orderly layers of This disrupts the orderly layers of atoms and makes it much harder for atoms and makes it much harder for the layers to slide over each other.the layers to slide over each other.


► Only small quantities of other elements need to Only small quantities of other elements need to be added to make a pure metal stronger and be added to make a pure metal stronger and harder.harder.

► Most metals used are alloys, because they are Most metals used are alloys, because they are tougher and stronger.tougher and stronger.

DURALUMIN

Copper + Aluminium

BRASS

Copper + Zinc

BRONZE

Copper + Tin/Aluminium

Metals: Chemical PropertiesMetals: Chemical Properties

► Reaction with WaterReaction with Water Metals react with water in varying degrees of Metals react with water in varying degrees of

intensity, to produce a intensity, to produce a metal hydroxidemetal hydroxide and and hydrogen gas hydrogen gas [[VIDEOVIDEO]]

Sodium + Water

Metals: Chemical PropertiesMetals: Chemical Properties

► Reaction with Hydrochloric AcidReaction with Hydrochloric Acid Metals also react with hydrochloric acid in Metals also react with hydrochloric acid in

varying degrees of intensity to produce a varying degrees of intensity to produce a metal chloridemetal chloride and and hydrogen gashydrogen gas

Metals: The Reactivity SeriesMetals: The Reactivity Series

► Not all metals react the same wayNot all metals react the same way Some react vigorously fast; others react slowly, Some react vigorously fast; others react slowly,

some don’t react at allsome don’t react at all

► Metals can be listed in order of reactivityMetals can be listed in order of reactivity The Reactivity SeriesThe Reactivity Series The most reactive metal is at the topThe most reactive metal is at the top

Metals: The Reactivity SeriesMetals: The Reactivity Series

►A metal high in the seriesA metal high in the series Reacts vigorously and quickly with Reacts vigorously and quickly with

chemicalschemicals Corrodes easilyCorrodes easily

►A metal low in the seriesA metal low in the series Does not react vigorously with chemicalsDoes not react vigorously with chemicals Does not corrode easily Does not corrode easily

Au Ag Cu [H] Pb Sn Fe Zn Al Mg Ca Na K

LeastReactive

MostReactive

Metals: Rusting of Iron & Metals: Rusting of Iron & SteelSteel

►Corrosion of iron and steel in air Corrosion of iron and steel in air rustingrusting

Iron + Oxygen Iron + Oxygen Iron (III) oxide Iron (III) oxide

2Fe + 3O2Fe + 3O22 Fe Fe22OO33

►ConditionsConditions Presence of water (moisture)Presence of water (moisture) Presence of oxygen (air)Presence of oxygen (air)

Metals: Prevention of RustingMetals: Prevention of Rusting

► Coating with layer of Coating with layer of another substance, another substance, stopping air/water stopping air/water from reaching the from reaching the iron/steel underneathiron/steel underneath Paint (cars)Paint (cars) Oil/Grease (machinery; Oil/Grease (machinery;

aids in lubrication)aids in lubrication) Once breached, Once breached,

rusting will still occurrusting will still occur


► Coating with another metal which corrodes in Coating with another metal which corrodes in place place Sacrificial protectionSacrificial protection Zinc (Galvanising; prevent rusting of ship hulls)Zinc (Galvanising; prevent rusting of ship hulls) Magnesium (prevent rusting of undersea steel pipes)Magnesium (prevent rusting of undersea steel pipes) Metal will rust in place even if coating layer is Metal will rust in place even if coating layer is

breachedbreached


MethodMethod UseUse

Covering with paintCovering with paint Large iron and steel Large iron and steel pipes e.g. cars, pipes e.g. cars, bridges, shipsbridges, ships

Covering with Covering with grease/oilgrease/oil

Machinery; aids in Machinery; aids in lubricationlubrication

Tin platingTin plating Canned foodCanned food

Chromium platingChromium plating Aesthetically pleasing Aesthetically pleasing because chromium is because chromium is

shinyshiny


MethodMethod UseUse

GalvanisingGalvanising Corrugated iron Corrugated iron sheets for roofingsheets for roofing

Zinc blocksZinc blocks Steel hulls of shipsSteel hulls of ships

Magnesium blocksMagnesium blocks Underground steel Underground steel pipespipes

Alloy (Steel)Alloy (Steel) Cutlery, medical Cutlery, medical instruments, kitchen instruments, kitchen

sinks, etcsinks, etc

Metals: The Extraction of Metals: The Extraction of MetalsMetals

►Metals seldom occur in nature in their Metals seldom occur in nature in their pure form pure form commonly found as commonly found as ores ores (ionic compounds of the metal + a (ionic compounds of the metal + a non-metal)non-metal) Bauxite (aluminium)Bauxite (aluminium) Cassiterite (tin)Cassiterite (tin) Galena (lead)Galena (lead) Haematite (iron)Haematite (iron)

Metals: The Extraction of Metals: The Extraction of MetalsMetals

► The rock is first removed The rock is first removed from the mineral and the from the mineral and the mineral is then purified via mineral is then purified via chemical meanschemical means Very reactive metals Very reactive metals

(electrolysis)(electrolysis)► E.g AluminiumE.g Aluminium

Moderately reactive metals Moderately reactive metals (heated with other (heated with other compounds)compounds)

► E.g. IronE.g. Iron Unreactive metals (found Unreactive metals (found

uncombined)uncombined)► E.g. goldE.g. gold

Metals: The Extraction of IronMetals: The Extraction of Iron

► Iron ore Iron ore haematitehaematite

► Extraction process Extraction process occurs in a occurs in a blast blast furnacefurnace where where temperatures can temperatures can reach over 1600 °Creach over 1600 °C



1.1. CokeCoke (carbon) reacts with (carbon) reacts with oxygenoxygen (air) to form (air) to form carbon dioxidecarbon dioxide & & heatheat

C (s) + O2 (g) CO2 (g)


2.2. Carbon dioxideCarbon dioxide reacts with more reacts with more cokecoke to form to form carbon monoxidecarbon monoxide..

C (s) + CO2 (g) 2CO (g)


3.3. Carbon monoxideCarbon monoxide reacts with iron reacts with iron (III) oxide to produce (III) oxide to produce molten ironmolten iron..

Fe2O3 (l) + 3CO (g) 2Fe (l) + 3CO2 (g)


4.4. LimestoneLimestone decomposes in heat to decomposes in heat to produce produce calcium oxidecalcium oxide and and carbon carbon dioxidedioxide..

CaCO3 (s) CO2 (g) + CaO (s)


5.5. ImpuritiesImpurities are present in the molten are present in the molten iron i.e. iron i.e. siliconsilicon, , sulphursulphur & & phosphorusphosphorus. . SiliconSilicon is found as is found as silicon dioxidesilicon dioxide (acidic) which reacts (acidic) which reacts with with calcium oxidecalcium oxide (basic) to form (basic) to form calcium silicatecalcium silicate (slag). (slag).

CaO (s) + SiO2 (s) CaSiO3 (l)

Metals: RecyclingMetals: Recycling

►Metals are a non-renewable resource Metals are a non-renewable resource Will not last forever Will not last forever Alternatives?Alternatives?

►Making use of other metals in placeMaking use of other metals in place►RecyclingRecycling


►Why Recycle?Why Recycle? Saves cost of metal extraction from oresSaves cost of metal extraction from ores Prevents unsightly dumping of unwanted Prevents unsightly dumping of unwanted

iron/steeliron/steel Prevents the leaching of harmful heavy Prevents the leaching of harmful heavy

metals into soilmetals into soil DisadvantageDisadvantage: Recycling metals can : Recycling metals can

sometimes be polluting.sometimes be polluting.


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15 Metals