P15

• Both air and water are needed for iron to rust
• providing a barrier between iron any air and water protects the iron from rusting
• Sacrificial protection provides a protection against rusting, the iron needs to be attached to a more reactive metal, (zinc, magnesium or aluminium)
• Rust is a form of iron oxide called hydrate iron oxide
• Galvanised iron is iron covered with a ayer of zinc as zinc is more reactive than iron
• Zinc has a stronger tendency to form positive ions by giving away electrons
• Alloys are harder than pure metals as in alloys the layers are distorted by differently sized atoms
• Bronze is an alloy of copper and tin
• Brass is an alloy of copper and zinc
• Alloys are tough and resistance to corrosion
• Gold can me made harder by adding other elements
• High carbon steels are very hard but brittle
• Low carbon steels are softer and easily shaped
• stainless steels are resistant to corrosion
• Thermosoftening polymers soften quite easily then reset when cooled
• Thermosoftening are made of individual polymer chains that are tangled together
• Thermosetting polymers do not melt when heated due to strong covalent bonds forming cross links between polymer chains
• Properties of a polymer depend on the monomers used to make it and the conditions carried out during the reaction
• LD and HD poly(ethene) have different properties as they are made using different reaction conditions and have different structures or different shaped molecules
• Borosilicate glass is made from sand and boron trioxide
• Clay are electrical insulators and resistant to chemical attacks
• Using reinforced concrete can be made more resistant to bending forces
• Haber process is used to manufacture ammonia to make fertilisers and other chemicals
• Raw materials needed to make ammonia like nitrogen from air and hydrogen from natural gas
• N2 + 3H2 <-> 2NH3
• The gases that come out of the reactor are cooled so the ammonia condenses
• The unreacted gases are recycled from the liquid ammonia so they are not wasted
• The nitrogen and hydrogen is compressed to a pressure of 200atm and heated to 450 celsius using an iron catalyst
• High temp will push the equilibrium to the less molecules and increase the yield
• High pressure is expensive and requires strong reaction vessels and pipes otherwise explosion risk
• Low temp with push equilibrium to the exo reaction and increase yield
• low temp the reaction is slow as the particles collide les often with less energy
• High temp favours the end reaction
• Catalyst has no effect on the position of equilibrium as it increases the rate forward and backward reaction equally
• Neutralisation is made to make ammonium phosphate
• You can make other fertiliser salts by reacting ammonia solution with different acids
• Most of the ammonia made in the HP is changed into compounds of ammonia used as fertilisers
• Crops need the nutrients nitrogen, phosphorus and potassium for healthy growth . NPK
• The source of phosphorus is deposits of phosphate containing rock
• Using a formulation to make a fertiliser so that they have specific properties