GCSE: OCR gateway: C2: Structure of the earth + construction materials

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  • C2
    • The Structure of the Earth
      • The Lithosphere
        • The crust and the top part of the mantle
        • Cold and rigid
        • Made up of tectonic plates which are less dense than the mantle below
        • Crust too thick to drill through so most imformation about the earth is obtained by seismic waves created by earthquakes and man made explosions
      • The Earth's Structure
        • Mantle cold and rigid below the crust however at greater depths is is non-rigid and able to move
        • The earth's core transfers energy so the temperature of the mantle increases with depth
          • Convection currents slowly move plates
        • Subduction
          • Oceanic crust is denser than continental crust
            • When plates collid the oceanic crust is forced down
              • Cooler at the margins than continental crust
              • Partly melts as it reaches the hotter part of the mantle
      • Plate Tectonic Theory
        • Scientists accept theory because  it explains a wide range of evidence + has been discussed and tested by many scientists
        • Wegener's theory not accepted at the time
      • Magma and Rocks
        • Magma rises through the crust as it is less dense forming volcanoes
          • Different types of magma composition make different kinds of eruptions
        • Geologists study volcanos to predict future eruptions + find out more about the earth's structure
    • Construction Materials
      • Raw Materials
        • Some raw materials are found in the earth's crust
        • Hardness can be compaired by rubbing two materials together
      • Rock Hardness
        • Sedimentary rock
          • Soft sediments compressed together so its soft
        • Metamorphic rock
          • Formed when sedimentary rock is changed by heat and pressure
            • Compressed into a mosaic of interlocking carbonate crystals
              • Makes it harder as it has been baked
        • Igneous rock
          • Formed when magma cools and solidifies
          • Granite has interlocking crystals so it is very hard
      • Cement and Concrete
        • Thermal decomposition
          • When a substance breaks down from heating to give two new substances
          • Calcium carbonate = calcium oxide + carbon dioxide
            • CaCO3 = CaC + CO2
        • Limestone heated with  clay makes cement
          • Mixing cement, sand, and small stones with water makes concrete
        • Composite materials
      • Reinforced Concrete
        • Under compression concrete is strong however under tension it is weak
          • If heavy loads are applied to a concrete beam the concrete will bend creating tension and compression
            • This cracks the concrete
        • Reinforced concrete is harder and more flexible than concrete so it is a better construction material


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