Metals, Extraction and Energy

• Exothermic reactions transfer energy from the reacting molecules to the surroundings. This means the temperature of the surroundings increases.
• Endothermic reactions take in energy from their surroundings. Temperature of the surroundings decreases.
• Activation energy- the minimum amount of energy particles must have in order to successfully collide with eachother.
• Collision theory states that chemical reactions only occur when there is enough kinetic energy between two particles so they can overcome the activation energy barrier
• Breaking chemical bonds is endothermic, making bonds releases energy, and is exothermic.
• When an ionic compound is melted or dissolved in water, the ions are free to move around. The compound can now conduct electricity. It is called an electrolyte.
• Negative electrode is the cathode, positive electrode is the anode. They are made of a conducting material such as graphite or a metal.
• Reduction reactions involve gaining electrons, loss of oxygen. Oxidation reactions involve losing electrons, gaining oxygen.
• In redox reactions, one substance is being oxidized while another is being reduced at the same time. This means that the substances involved in the reaction exchange electrons.
• First, aluminium oxide is mixed with cryolite which lowers the melting point and saves energy and money. It normally has a melting point of 2000c. The Al3+ ions are attracted to the negative cathode. Each ion gains three electrons and forms an aluminium. O2- ions are attracted to the positive anode. The anode must be replaced regularly as the oxygen reacts with graphite forming CO2.
• Al3+ + 3e- -----> Al (reduction)
• 2O2- - 4e- ----> O2 (oxidation)
• Electrolysis is very expensive as melting the compounds requires a great deal of energy and a lot of energy is required to produce an electric current.
• Iron ore (haematite) - Iron Oxide Fe2O3 is the compound in which the iron is extracted from.
• Coke- Used as a fuel and reacts to form carbon monoxide (needed to reduce the iron(III) oxide)
• Limestone (Calcium carbonate (CaCO3)- Helps to remove acidic impurities from the iron by reacting with them to form molten slag
• Hot Air (Oxygen (O2)Provides oxygen to allow the coke to burn.
• Step 1- Hot air (oxygen) reacts with the coke (carbon) to produce carbon dioxide and heat energy to heat up the furnace.

  C(s) + O2(g) → CO2(g)
• Step 2 – More coke is added to the furnace and reduces the carbon dioxide into carbon monoxide, a good reducing agent.

  CO2(g) + C(s) → 2CO(g)
• Step 3 – iron(III) oxide is reduced.

  iron(III) oxide + carbon → iron + carbon dioxide

  2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)
• The calcium carbonate in the limestone thermally decomposes to form calcium oxide.

  calcium carbonate → calcium oxide + carbon dioxide

  CaCO3(s) → CaO(s) + CO2(g)
• The calcium oxide then reacts with silica (sand) impurities in the haematite, to produce slag – which is calcium silicate. This is separated from the iron and used to make road surfaces.

  calcium oxide + silica → calcium silicate

  CaO(s) + SiO2(s) → CaSiO3(l)

  This reaction is a neutralisation reaction. 
• Electroplating is the process of coating an object with a thin layer of a different metal by electrolysis. The cathode is the object to be electroplated. The anode is made out of carbon or the metal being plated onto the object. The electrolyte is a compound containing the plating material.
• Copper must be purified to be used in wiring. The anode is impure copper, it loses electrons to from copper ions and these dissolve in the solution. These ions are attracted to the cathode and form copper metal. The cathode gains in size. Impurities in the anode fall to the bottom of the beaker as the anode dissolves away.
• At the cathode, if the metal is more reactive than hydrogen hydrogen gas will be produced. At the anode, if halide ions are present chlorine, bromine or iodine will be formed. If they are not, oxygen is formed
• Hydrogen makes a squeaky pop with a lighted splint
• Oxygen will relight a glowing splint
• In the electrolysis of brine, hydrogen gas is produced at the cathode and chlorine gas is produced at the anode. The sodium and hydroxide ions left over form sodium hydroxide.
• Different types of steel are made by varying carbon content. For example, mild steel (0.15-0.3% carbon) is malleable, ductile and easily shaped whilst hard carbon steel (0.7-1.5%) is harder but more brittle.
• We can test for the presence of transition metal ions by using a solution of sodium hydroxide. Copper- Blue precipitate Iron 2- green precipitate Iron 3- orange/brown precipitate
• Properties of transition metals- High melting + boiling point, malleable and ductile, high density, good electrical and thermal conductivity, useful catalysts, can form more than one type of ions and are often coloured.
• Factors which impact location: location near the coast in order to import raw materials, a site away from built up areas, a town or city within commuting distance to accommodate the workforce, good transport links for transporting the product to buyers, a direct electricity supply in the case of aluminium.
• The volume of the hydrogen formed is twice the volume of the oxygen formed, as there are two hydrogen atoms for every oxygen atom in a molecule of water (H2O).
• Aluminium- strong, low density, good conductor of heat and electricity, resistant to corrosion. It can be used in bicycle frames, aeroplanes, food cans and window frames
• Copper- very good conductor of heat and electricity, malleable and ductile, attractive colour and lustre. Can be used for decoration/ jewellery, electrical wiring, and heating systems.
• Titanium- hard, strong, low density, resistant to corrosion, high melting point. Can be used in bicycle frames and aeroplanes.
• Iron (steel)- strong and hard, however it corrodes easily. It can be used in gates and railings.
• Aluminium reacts very quickly with oxygen in the air to form aluminium oxide. A nice protective layer of aluminium oxide sticks to the aluminium below and stops any further reaction taking place.
• Combustion, neutralisation and oxidation reactions are all exothermic. Exothermic reactions are used in self-heating food cans and outdoor hand warmers.
• Thermal decomposition and electrolysis reactions are all endothermic. Endothermic reactions are used in instant ice packs used to treat injuries