Chemistry 5.3

• Metals are extracted from ores, which are minerals formed in the Earth's crust that contain metal compounds. Yet, some metals can be found in their natural (native) form in the ground.
• Titration


  A practical of neutralisation between an acid and an alkali (soluble base). The concentration of acid can be calculated with the use of alkali. This can be done the other way round.
• Method: An outline if an acid was being added to an alkali


  1. Step 1: Measure out a volume of alkali using a measuring cylinder or pipette and pipette filler to a clean conical flask (25cm³)

  2. Step 2: Add a few drops of indicator (Litmus) to the alkali and place on a white tile

  3. Step 3: Fill the burette with acid to 0cm³ and note the starting volume

  4. Step 4: Slowly add acid from the burette to the alkali, swirling to mix the two substances

  5. Step 5: Stop adding the acid when the end point is reached (when the colour changes). Note the volume of acid used to neutralise the alkali.
• Examples of metal ores


  • Haematite (iron oxide, Fe₂O₃)
  • Bauxite (aluminium oxide, Al₂O₃)
  • Malachite (copper carbonate hydroxide, Cu₂CO₃(OH)₂)
  • Galena (lead sulfide, PbS)
• Order of discovery of metals

  • Stone age - Gold, copper, silver found as elements (native) (Pre 3000BC)
  • Bronze age - Copper smelted and mixed with tin to make bronze (2000BC)
  • Iron age - Iron smelted to create weapons and tools (1000BC)
  • Aluminium age - Aluminium used to make objects that don't rust compared to iron and are light enough (1000AD)
• Order of reactivity from low to high

  • Gold, silver, copper, (hydrogen), iron, zinc, (carbon), aluminium, sodium
• The more reactive a metal is, the harder it is to extract it from its ore. Depending on its reactivity, a metal will be low reactivity, medium reactivity, or high reactivity.
• Displacement reactions


  A more reactive metal replaces a less reactive metal from a solution of one of its salts
• Displacement reactions


  • Magnesium + copper sulfate → Magnesium sulfate + copper
  • Calcium + iron chloride → Calcium chloride + iron
• Oxidation


  The gain of oxygen by a substance or the loss of electrons
• Reduction


  The loss of oxygen by a substance or the gain of electrons
• Whenever oxidation takes place, reduction can also happen, as for something to gain something, another thing must lose something. This is known as a redox reaction.
• In a redox reaction, the oxidation product becomes an ion with a small charge and a sign, while the reduction product becomes an element with no charge and no small number/sign.
• Thermite is a redox reaction, used to show displacement/oxidation/reduction and to join railway tracks together.
• Electrolysis


  The breaking up of a substance using electricity. For this to happen, the substance must be an electrolyte, which is an ionic substance (liquid or dissolved in water).
• Electrolysis process


  The positively-charged ions move to the cathode (negative) and receive electrons, becoming reduced. The negatively-charged ions move to the anode (positive) and lose electrons, becoming oxidised.
• Ions must be able to move freely for electrolysis to work, as they pass electrons to one another.
• Aluminium is the most abundant metal on Earth, but it's expensive, largely because of the amount of electricity used in the extraction process.
• Before the aluminium extraction process happens, aluminium oxide must be melted so that electricity can pass through it, yet with a high melting point of over 2000°C, it would be expensive. Instead it's dissolved in cryolite to about 900°C, this reduces the energy cost when extracting aluminium.
• The aluminium extraction process is located near a power station to have a reliable supply of the large amount of energy needed, near the coast to allow the import of raw materials, and near a town/city to allow workers to get there easily.
• Iron extraction in a blast furnace


  1. Step 1: Hot air (O₂) reacts with the coke (C) to produce carbon dioxide (CO₂) and heat energy to heat up the furnace

  2. Step 2: More coke (C) is added to the furnace and reduces the carbon dioxide (CO₂) into carbon monoxide (CO), a good reducing agent

  3. Step 3: Iron in reduced, to form element iron from the ionic form in the substance iron oxide

  4. Step 4: The calcium carbonate (CaCO₃) decomposes to form calcium oxide (CaO) which reacts with the silica impurity in the haematite to form calcium silicate
• Properties and uses of metals

  • Iron: Magnetised, conductor, low carbon - tough, ductile, malleable, corrosion resistant, high carbon - hard, strong, wear resistant, brittle, stainless - resilient to corrosion. Uses: Magnets, transformer cores, car body, panels, cutting tools, railway lines, cutlery and kitchen equipment
  • Aluminium: Strong, low density, conductor, resistant to corrosion. Uses: High voltage power lines, saucepans, windows and greenhouse frames, drink cans, aircraft and car parts
  • Copper: Good conductor, malleable, lustrous, attractive colour. Uses: Bronze and brass, water pipes, jewellery and ornaments, electrical wiring
  • Titanium: Hard, strong, low density, high melting point, resistant to corrosion. Uses: Jet engine and spacecraft parts, industrial machine parts, car parts, medical implants, sports equipment
• Alloy


  A mixture of two or more elements, with at least one being a metal. Alloys are used instead of pure metals as they are stronger due to the different types and amounts of metals used in the mixture.
• Examples of alloys


  • Brass (copper and zinc)
  • Bronze (copper and tin)
  • Stainless steel (iron, carbon and chromium)
• Between Group 2 and Group 3 in the periodic table, there is a section of metals known as 'transition metals' which are used in many compounds and can be found in the reactivity series.
• Transition metal properties


  • High melting and boiling points
  • Good conductors of heat and electricity
  • Malleable and can be easily beaten into shapes
  • Less reactive than the alkali metals (Group 1)
  • Hard and tough, with high densities
  • Form ions with different charges
  • Form colourful compounds