C3 Chemicals in our lives

C3 Chemicals in our lives

1. Evidence of changing Earth

   • Magnetic
     • Banding at constructive margins(Polarity swaps approx 500,000 yrs) shows continental drift
     • Angle of magnetic particles change polarity north to south of the equator
   • Sedimentary rock
     • Fossil remains: tell us what lived in different areas
     • Shells and ripples: show what lived in that area and whether it was desert or ocean
     • Grain shape: Desert = sandstone(coarse grain) Water = limestone(fine grain)
     • Tectonic plates: caused movement creating mountains + faults which exposed rock to weathering and erosion
     • Erosion: increased mineral sediment(salts) which dissolved and ran into shallow seas
       • As water evapourated the salts crystalised to form salt deposits(Under Cheshire)
     • Limestone formed when layers of sea creatures became buried and compressed
       • Limestone has a high calcium carbonate content from animal shells
     • Coal seams formed as a result of large swampland drying out and dead remains being buried and compressed
     • These resources(salts, limestone + coal) formed the basis of the chemical industry and it's postioning locally in the north west

2. Salt

   • Common salt is sodium chloride(NaCl)
   • We use sodium chloride for...
     • Preserving: Extending life of food
     • Flavouring: improving taste
     • Lowers melting point of ice
     • Chemicals: Extracting chlorine, Making hydrogen for ammonia + Making sodium hydroxide

3. Collecting salts

   • Sea salt
     • Mainly table salt
     • Almost 100% pure NaCl
     • Collected in large salt pans
   • Rock salt
     • Less pure 90% NaCl
     • Used on roads as grit
     • Mixture of salt and impurities(reddish clay known as halite)
   • Solution mining
     • Largely replaced underground mining
     • Salt produced is high purity 100%
     • Used for table salt
   • Stages of solution mining
     • 1) Water injected into salt deposits
     • 2) Salt dissolves to form brine clay(grit does not dissolve)
     • 3) Pressure drives brine back to the surface
     • 4) Brine refined by evapourating water + collect salt
   • Problems
     • Unregulated for 60yrs
       • Large holes lead to subsidence (1891 - Northwich chambers collasped)
     • Uses up finite resources(halite + fossil fuels)
     • Expensive use of energy to evapourate water

4. Salt in diet

   • We need salt in low quantities for...
     • Nervous conduction
     • Blood
     • Tears
   • Salt is added to food as...
     • Preservation: prevents fungal/bacterial growth
     • Flavouring: Enhances taste/flavours

5. Alkalis

   • Alkalis are a group of chemicals that dissolves in water to form OH- ions
   • Soluble hydroxides
     • Sodium hydoxide
     • Potassium hydroxide
     • Calcium hydroxide
   • Example: HCl + NaOH => NaCl + H2O
   • Importance of alkalis
     • Traditional uses
       • Neutralising acidic soil(lime added)
       • Soap making(convert fat to oils)
       • Fixing dyes
       • Making glass(sand, lime + soda ash)
     • Where alkalis come from...
       • Potash(burnt wood ash)
       • Roasting limestone in lime kilns
         • CaCO3 + heat => CaO + CO2
       • Le blanc process
         • 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

6. Importance of chlorine

   • Sewage can contain diseases such as
     • Cholera
     • Typhiod
     • Dysentry
     • Gastroenteritis
     • World health organisation(WHO) predict 3 million die a year from drinking contaminated water
   • Chlorine kills bacteria(helped water companies)
     • Reduction in typhoid cases
   • Where chlorine comes from...
     • From the Le blanc process: 4HCL + O2 => 2Cl2 + H2O
     • Today most chlorine is produced by electrolysis of brine(salt water)
   • Problems/concerns of chlorine
     • Surface water contains organic material(dead leaves)
     • Chlorine in water can react with matter to form Trihabmethanes(THMS)