Core Chemistry - Topic 2 Materials From The Earth

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  • Created by: Katie
  • Created on: 05-05-13 16:12

Rocks and their Formation

  • Igneous rocks - rocks formed by cooled, solidified magma
    • they contain interlocking crystals of different sizes
    • the size depends on the rate in which the magma cooled
    • slower rate = bigger crystals
    • longer time allows for them to grow
  • Sedimentary rocks - rocks formed from pieces of other rocks or hard parts of dead organisms
    • formed from sea shells made mostly of calcium carbonate e.g. chalk, limestone
    • layers of sediment build up on the sea bed and compact together over a long time
    • may contain fossils - remains of dead organisms or imprints e.g. footmarks
  • Metamorphic rocks - rocks formed by heating and/or pressurising existing rocks
    • marble is formed from chalk or limestone
    • the small gaps between the grains become new crystals of calcium carbonate that interlock tightly
    • meaning it is harder than chalk or limestone
  • Sedimentary rocks are the most susceptible to erosion
    • the interlocking crystals make rocks harder and less erodible
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Limestone and its Uses

  • Limestone is used:
    • as blocks to construct buildings 57%
    • a raw material to manufacture cement, concrete and glass 38%
    • making steal and iron alloys 5%
  • Limestone - out of the ground at a quarry
    • explosives used to break limestone into pieces
    • cut or crushed into useful size and exported
  • Thermal decomposition - strongly heating a compound so it decomposes
    • calcium carbonate - calcium oxide + carbon dioxide
  • Cement - heating limestone with powdered clay
    • found in mortar (used to hold bricks together)
  • Concrete - mixing cement with sand, gravel and water
    • used in construction of buildings/bridges
  • Glass - heating limestone with sand and sodium carbonate
    • chemical reaction occurs liquid glass is made
    • it cools and forms a hard transparent solid
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Advantages & Disadvantages of Quarrying Limestone

  • Advantages
    • provides jobs in difficult places (countryside)
    • helps local families and businesses
    • its valuable so helps local and UK economy 
    • provides a nature reserve after work is done
  • Disadvanages
    • ruin attractive scenery
    • dust and noise pollution
    • affect quality of life for locals
    • damage tourist industry
    • heavy lorries
    • extra traffic - pollution
    • land used cannot be used for farming etc
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Chemical Reactions

  • Atoms - smallest part of an element that can take part in chemical reacions
    • they make up all substances
  • Compound - atoms of 2 or more different elements chemically joined together
  • Chemical formula - shows symbols for elements present and ratios in which the are present
  • No atoms are created or destroyed in chemical reactions just rearranged ALL REACTIONS
    • total mass before = total mass after
  • The products have diffeent physical and chemical properties than the reactants
    • because their atoms are combined differently
  • Precipitation reactions - when soluble substances react together to form an insoluble product
    • called the precipitate
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Reactions of Calcium Compounds

  • Calcium oxide - one product of the thermal decomposition of limestone
    • calcium oxide + water = vigorous reaction making calcium hyrdoxide
    • releases lots of heat
    • calcium hydroxide - crumbly white solid
  • Limewater - calcium hydroxide dissolved in more water
    • turns from colourless to cloudy in presence of carbon dioxide
    • calcium        +      carbon        ➝      calcium       +      water
    • hyrdroxide            dioxide               carbonate
  • If a lot of carbon dioxide is bubbled through limewater - calcium carbonate disappears
    • colourless solution is formed
    • because carbon dioxide dissolves in water forming an acid solution
    • acid reacts with calcium carbonate 
  • Farmers may spray one on their crops as plants don't like acidic soil
  • Sulfur in coal - burns and produces sulfur dioxide (and nitrogen oxides)
    • both acidic gases that produce acid rain
    • wet calcium carbonate sprayed through waste gases to neutralise
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