Metals and their uses

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Extracting Metals

An ore is a metal compound deep underground that is worth extracting.This depends on:    How much of the metal the ore contain                                                                    How easy it is to extract the metal from its ore (e.g. the methods used for extraction e.g. electrolysis/ reduction / photomining etc)

From the last bullet point, you can tell that some ores can become worth extracting if new methods are discovered to extract an ore.Some metals, like gold and silver, are so unreactive that they exist purely as the metal itself; in their native state.

How a metal is extracted from its ore once the ore is harnessed really depends on where it lies in the reactivity series. If the metal is more reactive than carbon, the metal will have to be extracted through electrolysis. But if the metal is less reactive than carbon, it can be reduced and displaced from its ore to produce the metal itself and carbon dioxide.

metal oxide + carbon > metal + carbon dioxide                                    e.g. iron oxide (haematite) + carbon > iron + carbon dioxide

Some metals react with the carbon so we have to use something different to displace it e.g. Titanium becomes brittle if extracted using carbon as it reacts with the carbon, sodium or magnesium is used instead.

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Iron

Iron is less reactive than carbon so can used to reduce + displace it in a blast furnace

iron (iii) oxide + carbon > iron + carbon dioxide

Cast iron:

  • ·          Contain 96% iron
  • ·         The 4% impurities are mostly carbon
  • ·         Hard
  • ·         Brittle
  • ·         Can’t be easily compressed
  • ·         Can be run into moulds and cast into different shapes
  • ·         Used to make wood burning stoves, man hole covers on roads and engines

Pure iron:

  • ·         Very soft
  • ·         Easily shaped
  • ·         Not very useful
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Carbon Steels

Steel = Alloyed iron (an alloy is a mixture of metals)

Low carbon steels

  • · Contains less than 0.1% carbon
  • · Soft, easily pressed into shape
  • · Not as strong as HCSs
  • Used for car bodies, Knives, machinery, ships, containers, and structural steel for buildings.

High carbon steels

  • · Contains 0.1-1.5% carbon
  • · Very strong
  • · Brittle – likely to shatter
  • Used for car bodies, knives, machinery, ships, containers, and structural steel for buildings
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High and Low Alloy Steels

Low alloy steels

  • · Contain 1-5% of other metals
  • · Controlling amounts + type of metal > desirable properties
  • Use depends on alloy design

High alloy steels – e.g. Stainless Steels

  • ·   Contain a much higher percentage of other metals
  • ·   e.g . Chromium – Nickel
  • ·   Hard
  • ·   Strong
  • ·   Resistant to corrosion; do not rust
  • Used for cooking utensils/ Cutlery, chemical reaction vessels
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Aluminium

Aluminium:                                    

  • Silvery, shiny metal; attractive  
  • Surprisingly light; has a relatively low density    
  • An excellent conductor of energy + electricity                    
  • Malleable + Ductile      
  • Very resistant; does not corrode easily because of the thin layer of aluminium oxide it forms when in contact with the air, which stops any further reactions from taking place 
  • Strong and hard once alloyed                                                                          
  • Used for: coke cans, aluminium foil, saucepans, HV electricity cables, aeroplanes, space vehicles and bikes.

 

Extracted using electrolysis; a current is passed through molten aluminium at high temperatures to break it down. 

Aluminium ore is extracted.   >  •Aluminium is seperated  > •Aluminium is melted for  It contains loads of impurites      from the impurities                   electrolysis

Melting the alumiunim + electrolysis takes up lots of energy > costs a lot of money

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Titanium

Titanium:

  • A silvery-white metal; attractive
  • V. strong
  • V. resistent to corrosion; forms an oxide layer like aluminium to prevent any further reaction from taking place
  • Dense than aluminium, but not as dense as most metals, so still relativley light
  • Has a v. high melting point, so can be used as v. high temperatures
  • Used or high performance aircrafts and bikes (strong + light) , jet engines (retains strength at high temps) , nuclear reactors (high temps + resistent to corrosion) and replacement hip joints (light, strong + resistent to corrosion

Titanium oxide is seprated from its rock > Titanium oxide is converted into a chloride which is distilled to purify it > Titanium is displaced by Magnesium/Sodium

  • Titanium becomes brittle when carbon is used to displace it as it reacts with it so is then not of much use
  • Magnesium and Sodium have to be seperated by electrolysis in the first place. Each stage takes time and costs money
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