metals
DESCRIPTION
MetalsTRANSCRIPT
METALS
• Iron• Aluminium• Copper• Zinc• Magnesium
Properties of metals
• Strong , hard and dense• Solids at room temperature• High Melting point• Good electrical and heat conductors• Shiny • Malleable and ductile
Copper
• Ductile• Electrical conductors• Cooking utensils
Silver and Gold
• Non reactive• Malleable and ductile• Jewellery• Computer fibres
Iron and steel
• Strong and hard• Ships , bridges and buildings• ‘Rust’• Use antirust
Energy is needed to extract metals
Gold , silver highly non reactive , so present in their pure formMg,Na,Al ,Fe reactive Found in their ores
• MINING ( Ore From Ground) MILLING ( Crushing , Concentrating And Purifying) SMELTING ( Chemical Means) REFINING ( Purifying The Crude Metal)
IRON
• Hematite ( )• Magnetite ( )• Siderite ()• Limonite• Iron pyrites
SMELTING
+ C Fe + C
[SMELTING] FOR LOWER MP metals ( Fe , tin , Cu)800 degree C , low oxygen content environment
PURIFYING METALS USING ELECTRICITYAnode Impure MetalConducting solution( electrolyte)Cathode Pure Metal
Impurities dropped inside the vessel ( non conductors)
ALUMINIUM
Most abundantExtracting it is a difficult taskMany historical methods of extracting aluminiums i) Heating in the presence of potassium mercury amalgam
Uses of Aluminiumi) Aircrafts & defence ( Light weight and strong)ii) Doesn’t corrode as the self healing oxide helps against rustingiii) Paper foils
Charles Hall Method of Al extraction
Dissolving Alumina in the mineral cryolite
℃
Alloys
Pure metals Soft and brittle , quite reactiveAlloy Mixture of two or more elementsProportion of metals in a given alloy can change
STEEL IRON and CARBONBRASS COPPER and ZINCBRONZE COPPER and TINDURALUMIN Aluminium and Tin
STEEL
IronCopper (0.2-2.4% by weight)
Hardening agentsManganeseChromiumTungsten
STEEL
Stainless Steel 10% chromium , magnetic/non magnetic
Increasing the carbon content can make the strength higher
Carburising A process of increasing the amount of carbon in steel by 0.5-1% to make it hard.
BRASS
Copper and Zinc
Decorationlocks , gears , bearings and valvesPlumbing and electrical equipmentMusical instruments
More malleable than either copper or zinLow MP , recycleAddition of ‘Aluminium’ makes it stronger and corrosion resistant
SOLDER
Fusible Metal alloyTin and LeadMelting Point 90-150 ℃Join metallic surfaces , plumbing , electronics soldering
Bronze
• Copper (90%) and Tin (10%)• Weapons• Musical instruments and weapons
Gold and other alloys
Gold -> Softer as compared to other alloysSterling silver Silver and CopperPlatinum Pure form , ductile , but if you add cobalt or iridium it becomes stronger
Reactivity of Metals
Reaction with dilute acid
Ca > Mg > Zn > Cu
Bubbles of hydrogen gas Effervesces
Reactivity of Metals
Reaction with waterSodium when kept in air MOISTURE TarnishIt is stored in air-tight containers
Na , K , Li ,Ba and Ca React with water
Al , Zn and Fe react with steam
Cu , Ag , Au , Pt , Sn , Pb Don’t react with water
Reactivity of Metals
Reaction with oxygen
Ag , Au and Pt Don’t react with oxygen
Burn rapidly in air K , Na , Ba , Ca , Mg
Reacts slowly Zn , Fe ( rusting)
Very slowly Al , Cu , Hg
Balance the reactions
Mg + HCl + Na + NaOH + Ca + CaO
Order of reactivity
Mg > Al > Zn > Fe > Pb > Cu
More reactive the metal , more stable the carbonate
Difficult to decompose the carbonate if it is highly stable
MgC is stable the CuC
Activity Series of Metals
K Na Ca Mg Al Zn Fe Sn Pb Cu Ag Pt Au
RED Metals requiring electrolysisBlack Reduced by C or CO
Activity Series of Metals
Acid on Metal Hydrogen gas and Salts
Oxygen/Air on Metal Produces oxides and burns
Sacrificial Electrodes
Coating of Zinc over the cast iron motor body prevents it from rusting.
Since Zn is more reactive than Fe , it corrodes faster
First Ionization Energy
The first ionisation energy is defined as the energy required to remove one mole of electrons from one mole of gaseous atoms to provide one mole of gaseous single charged ions.
Na(g) --> Na+(g) + 1e
• Subsequent ionisation energies are defined in a similar way only by removing electrons from already charged ions.
First Ionization Energy
• Group 14
Mole
Avogadro's Number 6.022 x (NA)
Number of atoms in 12grams of Carbon -12 isotope
Number of moles = Number of particles / Number of particles in one mole
n = N / NA
Moles
Number of moles = mass of the given substance / Mass of one mole
Moles Grams (Molar Mass )Number of particles ( NA)
Conservation of volume
The pressure of a gas of fixed mass and fixed volume is directly proportional to the gas's absolute temperature.