Chemistry - Unit 1

chemistry notes

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  • Created by: tanya
  • Created on: 28-03-10 21:21

Atoms, Elements and Compounds

  • All substances are made of ATOMS.
  • substances made up of only one atom are called ELEMENTS
  • elements are arranged in the periodic table in vertical columns called GROUPS
  • different atoms join together to form COMPOUNDS
  • atoms are made up of tiny central NUCLEUS with ELECTRONS orbiting around it
  • two or more atoms bonded together are called a MOLECULE
  • different atoms bond together by GIVING, TAKING or SHARING ELECTRONS
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Limestone and its uses

  • limestone is made up of mainly CALCIUM CARBONATE
  • POWDERED LIMESTONE can be heated with SAND and SODIUM CARBONATE (soda) to make GLASS
  • POWDERED LIMESTONE can be heated with POWDERED CLAY to make CEMENT
  • when CEMENT POWDERED, WATER, SAND and CRUSHED ROCKS are mixed together a slow reaction takes place to produce CONCRETE
  • when we heat LIMESTONE strongly it breaks down to form QUICKLIME (calcium oxide)
  • CARBON DIOXIDE is also produced from this process
  • breaking down a chemical by heating is called THERMAL DECOMPOSITION
  • to make lots of QUICKLIME the reaction is done in a LIME KILN
  • calcium carbonate ----(heat)--- calcium oxide + carbon dioxide
  • LIMESTONE is widely used in BUILDINGS

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Qiucklime and Slaked Lime

  • when we add water to quicklime it reacts to produce SLAKED LIME (calcium hydroxide) and it gives out a lot of HEAT
  • calcium oxide + water ------ calcium hydroxide CaO + H2O ------ Ca(OH)2
  • we can dissolve calcium hydroxide in water and filter to produce LIMEWATER
  • LIMEWATER goes cloudy when CARBON DIOXIDE is added as CALCIUM HYDROXIDE is produced
  • calcium hydroxide + carbon dioxide ------ calcium carbonate + water Ca(OH)2 + CO2 ------ CaCO3 + H2O
  • MORTAR can be made by adding SLAKED LIME, SAND and WATER
  • MORTAR is used for building as it reacts with the CARBON DIOXIDE in the air producing CALCIUM CARBONATE again
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Cement, Concrete and Glass

  • heating LIMESTONE with CLAY in a kiln produces CEMENT
  • when we mix LIMESTONE, CLAY and OTHER MINERALS and then heat and grind into a fine powder PORTLAND CEMENT is produced
  • pouring CONCRETE around STEEL RODS or BARS then allowing to set strengthens the CONCRETE. this is called REINFORCED CONCRETE
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Extracting Metals

  • the EARTHS CRUST contains lots of metals
  • a rock containing enough of a metal is called a metal ORE
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Mr Wow

Make sure you say elements are made up of only one TYPE of atom. You may lose marks for saying made up of one atom.

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