Rocks & Building - AQA Chemistry C1a

The first section out of three from AQA chemistry C1a.

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  • Created by: Amy
  • Created on: 15-05-10 18:26

Atoms, elements and compounds

  • All substances are made up of atoms.
  • If a substance is only made up of one type of atom, we call it an element.
  • There are around 100 elements, all shown in the periodic table.
  • Each group of the periodic table contains elements with similar properties.
  • Elements are represented by symbols.
  • Atoms have a small central nucleus, made up of protons and neutrons, which is surrounded by electrons.
  • Compounds are made up of two or more types of atom which have reacted together.
  • Atoms react to form compounds by giving, taking or sharing electrons.
  • Atoms in compounds are held together by chemical bonds.
  • No atoms are made or lost in a reaction so the mass of the products is the same as the mass of the reactants. This is why symbol equations must be balanced.
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Limestone and its products 1

  • Limestone is mostly made of calcium carbonate (CaCO3)
  • Limestone can be quarried and used as a building material
  • Thermal decomposition is breaking down using heat
  • Calcium carbonate can be decomposed by heating to make quicklime, which is also known as calcium oxide (CaO), and to make carbon dioxide (CO2)
  • Carbonates of other metals can be decomposed in a similar way
  • Quicklime is reacted with water to produce slaked lime - calcium hydroxide (Ca(OH)2)
  • Quicklime can be made in a furnace called a lime kiln
  • Slaked lime, mortar, cement, concrete and glass all come from limestone
  • We can dissolve slaked lime in water and filter to get lime water
  • Slaked lime is reacted with carbon dioxide to get limestone and water
  • Mixing slaked lime with sand and water gives us mortar, which is used as a building material
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Limestone and its products 2

  • Heating limestone with clay in a kiln produces cement
  • Portland cement is made from a mixture of limestone, clay and other minerals which are heated and ground into a fine powder
  • Modern houses are made from a mixture of Portland cement and sand, which sets when it is mixed thoroughly with water and left for a few days
  • A mixture of water, cement and sand has stones or crushed rocks added to it to form concrete when it sets.
  • Concrete can be made even stronger by pouring it around steel rods or bars and leaving it to set. This is reinforced concrete.
  • Glass is made when powdered limestone is mixed with sand and sodium carbonate and heated strongly
  • Glass allows us to make buildings both weatherproof and light.
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