C3 : Chemicals in our lives

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How were rocks made?

  • The Outer layer of the earth is made up of 12 Tectonic plates
  • Convection currents under the plates make them move.
  • Scientists use magnetic clues in rocks like Magnetite to track continents' movements.
  • These processes form rocks:
  • Sedimetation and Compression - Limestone when remains of dead sea animals fell to the bottom of warm seas near the equator.
  • Erosion of rocks by rivers formed sand, this was deposited in layers to form Sandstone.
  • Evaporation of seas formed Rock salt. Salty water was orginally salts from rocks dissolved in water flowing over them.
  • Mountain building pushed coal towards the surface- the coal formed when plants in swamps died and were compressed and heated
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How do we know how rocks were made?

  • Different Animals lived at different times, their Fossils tell of the age of the rocks they are in.
  • Comparing Sand grains in Deserts and Rivers to those in Sandstone tell what sort of sand formed the stone.
  • Shapes of Ripples in rocks give clues about whether Sandstone was from River bed or Desert sand.
  • Shell Fragments in Limestone tell of the conditions when the rock formed.
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Where does salt come from?

  • Salt (Sodium Chloride) is used in Food, to Treat icy roads and in Chemical Synthesis.
  • Salt for Foods must be Pure. Some of it comes from the Sea; water Evaporates, leaving salt behind.
  • Rock salt - A Mixture of Salt and Clay. Used for de-icing roads, need not be Pure. It's mined from Underground with big machines.
  • Salt for Chemical Industry must be Very Pure. It's obtained from Solution Mining: water pumped into Rock salt, salt Dissolves in water, Solution pumped to surface, Solid salt is Extracted from the solution
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Why is Salt added to Food?

  • Flavouring - Improves flavour of the food.
  • Preservative - Stops food going off.
  • Eating too much salt can raise your Blood Pressure; this increases the risk of a Stroke or Heart attack.
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Why are Alkalis useful?

  • Before industrialisation, they were used to:
  • Neutralise acid soil.
  • Make chemicals to Bind dyes to cloth.
  • Convert Fats and Oils into Soaps.
  • Make Glass.
  • Alkalis dissolve in water to form solutions of Ph above 7.
  • They react with acids to form Salts:
  • Sodium Hydroxide + Hydrochloric acid = Sodium Chloride + Water
  • Alkalis include soluble Hydroxides and soluble Carbonates.
  • Soluble Hydroxides react with acids to form a Salt and Water
  • Sodium Hydroxide + Sulfuric Acid = Sodiumm sulfate + Water 
  • Soluble Carbonates react with acids to make a Salt, Water and Carbon Dioxide
  • Sodium Carbonate + Hydrochloric acid = Sodium chloride + Water + Carbon dioxide.
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How were Alkalis obtained?

  • Pre-Industrial Revolution - From burnt wood and stale urine.
  • Industrial revolution - New way invented to make Alkali on a large scale.
  • Raw materials: Salt (Sodium Chloride), Limestone (Calcium carbonate) and Coal.
  • Made huge amounts of pollutants: Acidic Hydrogen Chloride gas, Solid waste which emitted toxic, smelly Hydrogen sulfide gas.
  • Henry Deacon used Hydrogen chloride to make Chlorine by Oxidising it.
  • Hydrogen chloride + Oxygen = Chlorine + Water.
  • Chlorine is used as a bleach and to whiten paper and textiles.
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Why add Chlorine to Water?

  • Chlorine kills pathogens in water.
  • Adding Chlorine to Water leads to fewer deaths from waterborne diseases.
  • Disadvantage: When Chlorine reacts with organic matter THMs may form and people think that drinking water containing these can cause cancer.
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What does Brine make?

  • Passing electricity through brine (sodium chloride solution) causes chemical changes.
  • The elements in Sodium chloride and Water are rearranged to form new products.
  • Chlorine gas - Used to treat water, make bleach, plastic and Hydrochloric acid.
  • Hydrogen gas - A fuel, make Hydrochloric acid.
  • Sodium hydroxide solution - Used to make soap, paper and bleach.
  • If the electricity is generated from fossil fuels, much pollution results.
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Are chemicals risky?

  • There are 12 synthetic chemicals which are banned because everyone agrees that they are harmful evem in small amounts.
  • They cause problems because:
  • They don't break down in the environment.
  • They travel long distances in the air and in water.
  • They build up in the fatty tissue of animals and humans.
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What are the dangers of PVCs?

  • PVC molecules are made up of Carbon, Hydrogen and Chlorine.
  • Hard PVC - Window frames, water pipes.
  • Soft PVC - Wire insulation, Clothing.
  • PVC film - Hospital blood bags and drip bags.
  • PVC is softened using Plasticisers. They are very small and can escape from the plastic and dissolve in liquids in contact with it.
  • Plasticisers are linked to Cancer and Infertility.
  • In the EU some plasticisers have been banned from children's toys.
  • The PVC makers say they do not harm anyone.
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