C3 Chemicals in our lives

Evidence of changing Earth
1. Magnetic
  1. Banding at constructive margins(Polarity swaps approx 500,000 yrs) shows continental drift
  2. Angle of magnetic particles change polarity north to south of the equator
2. Sedimentary rock
  1. Fossil remains: tell us what lived in different areas
  2. Shells and ripples: show what lived in that area and whether it was desert or ocean
  3. Grain shape: Desert = sandstone(coarse grain) Water = limestone(fine grain)
  4. Tectonic plates: caused movement creating mountains + faults which exposed rock to weathering and erosion
  5. Erosion: increased mineral sediment(salts) which dissolved and ran into shallow seas
    1. As water evapourated the salts crystalised to form salt deposits(Under Cheshire)
  6. Limestone formed when layers of sea creatures became buried and compressed
    1. Limestone has a high calcium carbonate content from animal shells
  7. Coal seams formed as a result of large swampland drying out and dead remains being buried and compressed
  8. These resources(salts, limestone + coal) formed the basis of the chemical industry and it's postioning locally in the north west
Salt
1. Common salt is sodium chloride(NaCl)
2. We use sodium chloride for...
  1. Preserving: Extending life of food
  2. Flavouring: improving taste
  3. Lowers melting point of ice
  4. Chemicals: Extracting chlorine, Making hydrogen for ammonia + Making sodium hydroxide
Collecting salts
1. Sea salt
  1. Mainly table salt
  2. Almost 100% pure NaCl
  3. Collected in large salt pans
2. Rock salt
  1. Less pure 90% NaCl
  2. Used on roads as grit
  3. Mixture of salt and impurities(reddish clay known as halite)
3. Solution mining
  1. Largely replaced underground mining
  2. Salt produced is high purity 100%
  3. Used for table salt
4. Stages of solution mining
  1. 1) Water injected into salt deposits
  2. 2) Salt dissolves to form brine clay(grit does not dissolve)
  3. 3) Pressure drives brine back to the surface
  4. 4) Brine refined by evapourating water + collect salt
5. Problems
  1. Unregulated for 60yrs
    1. Large holes lead to subsidence (1891 - Northwich chambers collasped)
  2. Uses up finite resources(halite + fossil fuels)
  3. Expensive use of energy to evapourate water
Salt in diet
1. We need salt in low quantities for...
  1. Nervous conduction
  2. Blood
  3. Tears
2. Salt is added to food as...
  1. Preservation: prevents fungal/bacterial growth
  2. Flavouring: Enhances taste/flavours
Alkalis
1. Alkalis are a group of chemicals that dissolves in water to form OH- ions
2. Soluble hydroxides
  1. Sodium hydoxide
  2. Potassium hydroxide
  3. Calcium hydroxide
3. Example: HCl + NaOH => NaCl + H2O
4. Importance of alkalis
  1. Traditional uses
    1. Neutralising acidic soil(lime added)
    2. Soap making(convert fat to oils)
    3. Fixing dyes
    4. Making glass(sand, lime + soda ash)
  2. Where alkalis come from...
    1. Potash(burnt wood ash)
    2. Roasting limestone in lime kilns
      1. CaCO3 + heat => CaO + CO2
    3. Le blanc process
      1. Salt + sulphic acid from pyrites(iron sulphide)
        Hydrogen chloride gas
        Salt cake(sodium sulphide) + Coal(carbon) + Limestone(calcium carbonate)
        Alkali soda ash(sodium carbonate)
        Sodium waste
Importance of chlorine
1. Sewage can contain diseases such as
  1. Cholera
  2. Typhiod
  3. Dysentry
  4. Gastroenteritis
  5. World health organisation(WHO) predict 3 million die a year from drinking contaminated water
2. Chlorine kills bacteria(helped water companies)
  1. Reduction in typhoid cases
3. Where chlorine comes from...
  1. From the Le blanc process: 4HCL + O2 => 2Cl2 + H2O
  2. Today most chlorine is produced by electrolysis of brine(salt water)
4. Problems/concerns of chlorine
  1. Surface water contains organic material(dead leaves)
  2. Chlorine in water can react with matter to form Trihabmethanes(THMS)

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C3 Chemicals in our lives

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	Criado por Aaronbeaumont mais de 12 anos atrás