Chemistry, 10: Metals

• What are the properties of metals?

  Shiny

  High melting point

  Good conductor of heat and electricity

  Sonorous

  Ductile

  Malleable

  Shiny

  *Exclusion of alkali metals that have low m.p and not sonorous

  *Mercury has a low m.p as well
• Metals are giant structures of atoms arranged in a regular pattern making them a good conductors of heat and electricity
• Metal atoms give up one or more electrons to form cations, positive ions
• In metals, negative electrons are attracted to the positive ions holding the structure together
• In metals, electrons are free to move and are delocalised. It is not fixed in one position.
• Metals are good conductors because the delocalised electrons are free to move through the structure

  Then in circuit, electrons can move towards positive terminal and negative terminal supplies electrons
• Metals are ductile and malleable because the bonds are not as rigid, the ions can move around in different positions as well.
• Alloys are a mixture of a metal with one or more element

  It improves the properties of the metal
• What are some alloys and how they are improved?

  Steel, hard and tensile

  Bronze, hard

  Solder, low m.p

  Cupronickel, cheaper than nickel

  Stainless steel, resistant to corrosion

  Brass, easier to shape and stamp
• Because alloys are made from different size atoms, it is harder for atoms to move over making it more resistant to scratching and indentations.
• More reactive metals react with oxygen to form oxides
• Less reactive metals do not react with oxygen
• The more reactive a metal is:

  • The easier is to form a compound
  • The harder it is to break the compound
• More reactive metals react with water at room temperature

  E.g. potassium, sodium, calcium
• Less reactive metals react with steam

  E.g. magnesium, iron
• Mid-reactivity metals produce hydrogen when reacting with dilute acids

  E.g. magnesium, zinc, iron
• Metals below hydrogen do not react to form hydrogen with water or dilute acids
• Elements below carbon can be obtained by heating the oxide with carbon

  This is displacement reaction as the more reactive metal is reduced by carbon, and the carbon becomes oxidised
• More reactive metals form ions more readily than less reactive metals

  Any element higher up in reactivity can displace an element lower down
• More reactive elements can push a less reactive out of a compound
• Metals can be found as ores, containing minerals mixed with unwanted rocks
• Only gold can exist in a naturally pure state
• In almost all other cases, mineral is a compound of the metal
• To extract a metal from its ore:

  • Physically separate the mineral from the unwanted rock
  • Chemically break down the mineral to obtain the metal
• Extracting iron is done in a large scale by reduction using carbon in a blast furnace
• What are the 3 important raw materials put in the top of the blast furnace when extracting iron?

  1. Iron ore, iron (II) oxide which is also known as haematote
  2. Coke, source of carbon for reduction which is nearly pure
  3. Limestone, removes impurities as slag
• Describe the process of iron extract:

  1. Crushed up iron ore, coke, and limestone fed into the top
  2. Hot air is blasted up from the bottom
  3. Oxygen from air reacts with coke to form carbon dioxide
  4. Carbon dioxide reacts with coke to form carbon monocide
  5. Carbon monoxide is a reducing agent, iron (III) oxide is reduced to iron
  6. Dense molten iron runs to the bottom as runoff
  7. !intestine is broken down by heat to calcium oxide
  8. Calcium oxide reacts with impurities like sand (silicon dioxide) to form slag
  9. Slag is runoff and tapped off
• What is the overall equation of iron extraction?

  Iron (III) oxide + carbon -> iron + carbon dioxide

  2Fe2O3 (s) + 3C(s) -> 4Fe(s) + 3CO2(g)
• Describe the iron extraction in three key stages:

  1. Coke reacts with oxygen blasted into the furnace

  Carbon + Oxygen -> Carbon dioxide

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

  2. Carbon dioxide is reduced by unreacted coke to form carbon monoxide

  Carbon dioxide + carbon -> carbon monoxide

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

  3. Iron (III) oxide is reduced by carbon monoxide to iron

  Iron (III) oxide + carbon monoxide -> iron + carbon dioxide

  Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g)
• Iron is brittle, as it contains a large % of carbon

  This means that it rusts easily as well
• Iron is converted to steel, an alloy of riom
• In steel making, molten iron straight from the blast furnace is heated

  Oxygen is passed through to remove some carbon present

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

  Limestone (CaCO3) is added and changed into calcium oxide

  CaCO3 -> CaO(s) + CO2Z(g)

  The calcium oxide reacts with oxide impurities to form slag that can removed from steel

  CaO(s) + SiO2(s) -> CaSiO3(s)
• Steel has <2% of carbon content

  It is more resistant to corrosion

  It is less brittle can iron
• Stainless steels can be made by adding other metals

  E.g. chromium, nickel, vanadium, cobalt
• Reactive metals (above carbon) is removed by electrolysis
• Less reactive metals (below carbon) are obtained by heating the oxide with carbon as it is reduced into the metal
• Recycling is economically and environmentally beneficial

  This can be melting metal to form new objects
• What are the uses of aluminium?

  Used based on low density

  Used for manufacture of aircraft

  Used for food containers, as it does not corrode
• Why is the un-reactivity of aluminium beneficial?


  It does not react with acids

  Resistant to corrosion

  Has a thin coating of Aluminium oxide (Al2O3)

  Aluminium oxide is very un-reactive, protecting the aluminium below
• Zinc creates the alloy brass by mixing with copper