C2

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  • C2
    • Construction Materials
      • Rocks
        • Marble: Metamorphic, made from limestone under great heat & pressure over a long period of time
          • Shiny, hard
          • Usually found deep underground
        • Granite: Igneous, molten rock which has cooled and solidified
        • Chalk: Soft, powdery, white, found near Earth's surface
      • Clay makes bricks
      • Sand + limestone --> glass
      • Limestone
        • Thermal de-composition: breaking a substance down by heat into 2 or more substances
        • CaCO3 --> CO2 + CaO
          • CaO + H2O   --> Ca(OH)2
            • Ca(OH)2 + CO2 --> CaCO3 + H2O
        • Uses
          • Building stone
          • Toothpaste
          • Bread
          • Neutralising acid soil
          • Glass
          • Lime
          • Cement
          • Iron
        • CaCO3 + H2SO4 --> CaSO4 + CO2 + H2O
        • CaCO3 + 2HNO3 --> Ca(NO3)2 + CO2 + 2H2O
      • Cement: powdered clay + powdered limestone - mixed & heated
      • Limestone + iron ore --> iron
      • Sand + cement + aggregate     --> (water, chemical reaction) concrete
        • Cement bonds agregate + sand; liquid concrete: then poured over steel bars or mesh to reinforce concrete
          • Reinforced concrete: better construction material
            • Has flexibility of steel, so doesn't break under tension
            • Has hardness of concrete
          • Can be imported in earthquake areas
    • Making Cars
      • Rusting
        • Only steel + Fe rust
        • Fe: rust forms in tiny flakes + damp air can attack metal below
          • In time, it rusts all the way through
        • Fe + O + H2O --> Hydrated Fe (3) Oxide
        • Al: thin coat of Al2O3 forms (tenacious), so protects it from oxygen
      • Materials
        • Al car body + hub caps
          • Low density, malleable, doesn't corrode
        • Cu electrical wiring
          • Ductile, good electrical conductor
        • Pb-acid battery
          • Chemical reaction produces electricity
        • Plastic dash-board, bumper
          • Rigid shape, cheap, doesn't corrode
        • Textile fibres in seats
          • Can be woven + dyed, hard-wearing
        • PVC Wire covering
          • Electrical insulator, flexible
        • Glass/plastic composite in windscreen
          • Transparent, doesn't shatter
      • Al v. Steel
        • Al2O3: impervious (won't let oxygen in to react with Al)
        • Al2O3: tenacious (won't flake off Al)
        • Al: lighter than Fe
        • Mineral cryolite helps extract Al from ore
        • Al: corrode less, lighter, more expens-ive than steel, better fuel economy, longer lifetime
      • Recycling
        • EU law will soon require 95% of car to be recyclable
        • Makes sense because...
          • Al, Fe + Cu ores are finite sources
          • Saves energy + land needed for landfill + avoids environmental damage from mining
          • Plastic: made from non-renewable crude oil
          • Recycling batteries stops toxic materials entering environment
        • Difficulties
          • Expensive to sort all differ-enf materials
            • Different alloys + metals
            • Range of polymers (plastics) used
    • Superconduct-ors: materials that have no or little resistance
      • Current: flow of electrons
      • Only work at ~-200C; to be useful, they should work at 20C, room temperature
      • Can be used in electricals
      • Resistance stops currents from flowing in a circuit
      • Metals have many free electrons, so currents can flow easily through them (low resist-ance)
        • So they are good electrical conductors
        • Insulators: opposite
      • Benefits
        • Fast electronic circuits
        • More powerful electro-magnets
        • Electricity can be transmitted through wires with no power loss
    • Acids + Bases
      • Indicators
        • Contain dyes which change colour with pH
        • Single indicators change colour suddenly at particular pH
        • Different indicators change colour at different pH
        • Universal indicator: mixture of dyes, changes colour grad-ually with pH
      • All acids form H+ ions in water
      • pH of acid depends on concentration of H+ ions
        • Higher H+ ion concentra-tion: lower pH
      • Alkali: soluble base
      • Alkalis form OH- ions in water
      • Equations
        • Acid + base   --> salt + H2O
        • Acid + metal carbonate --> salt + H2O + CO2
        • Key ionic equation for neutralisation: H+ + OH- --> H2O
        • Acid + NH3   --> ammonium salt
      • Neutralisa-tion: H+ ions react with OH- ions to make neutral water
    • Fertilisers + Crop Yields
      • % error: (error in apparatus / volume) * 100%
      • % of N: (#atoms of N in compound * 14 / RFM of compound) * 100%
      • Larger volume = lower % error
      • Mass of reactants = mass of products
      • Fertilisers
        • HNO3 + NH3 --> NH4NO3
        • 3H3PO4 + 9NH3 --> 3(NH4)3PO4
        • H2SO4 + 2NH3 --> (NH4)2SO4
        • HNO3 + KOH --> KNO3 (+ H2O)
        • Advantage: increases crop yield
        • Problem: eutrophication
        • Making them in a lab
          • Measuring cylinder to measure a particular volume of an alkali solution
          • burette to add acid a little at a time
          • Filter funnel to remove solid crystals of fertiliser from solution
      • (Mass given / its Mr) * Mr of what you need to find

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