AQA SCIENCE C1A)

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C1A 1.1 ATOMS, ELEMENTS AND COMPOUNDS

ATOMS

 atom (http://scienceaid.co.uk/chemistry/fundamental/images/atom.jpg)

  • everything is made of atoms
  • there are over 100 types of atom which gives us millions of substances
  • atoms are made up of a nucleus with electrons around it
    • the nucleus is made up of neutron and protons
    • protons have a positive charge and electrons have a negative charge
      • the number of protons = number of electrons so atoms have an overall neutral charge

ELEMENTS

  • substances made of only one type of atom is called an element
  • all elements have their own symbol
  • element are put into order of size and grouped by properties in the periodic table

COMPOUNDS

  • most substances are compounds
    • this means they are made up of more than one type of atom
  • atoms in a compound have chemical bonds making them difficult to separate
    • with ionic, atoms lose or gain electrons to fill their outer shells so become charged which attracts them to oppositely charged atoms
    • with covalent, atoms share electrons to fill their outer shells

C1A 1.2 LIMESTONE AND ITS USES

  • Limestone is a rock made mainly of calcium carbonate 
  • its chemical formula is CaCO

USES

  • building blocks - St Paul's Cathedral
  • processed into glass
  • processed into concrete and cement

PROCESSING

  • Thermal Decomposition
    • CaCO3 >>> CaO + CO2
  • Lime Kiln
    • this thermal decomposition can be done on a large scale in a rotary kiln

C1A 1.3 DECOMPOSING CARBONATES

  • some other carbonates decompose like limestone in a Busen flame

BALANCING EQUATIONS

  • Symbols are used in equations to make them simpler and easier to understand internationally
  • the same amount of mass must be on either side of the equation
  • sometimes numbers are put in front of a molecule's symbol to balance the equation

C1A 1.4 QUICKLIME AND SLAKED LIME

SLAKING LIME

  • When limestone is thermally decomposed, one of the products is quicklime
  • when water is added to quicklime it makes slaked lime
    • CaO + H2O >>> Ca(OH)2 
    • This reaction is very exothermic
  • Dissolving slaked lime in water makes lime water

MORTAR

  • made by adding water and sand to slaked lime
  • used to hold buildings together because the lime water reacts with the carbon dioxide in the air, turning it to stone

C1A 1.5 CEMENT, CONCRETE AND GLASS

CEMENT

  • heating limestone with clay makes cement
  • this sets even underwater, unlike mortar
  • this makes it much more useful

CONCRETE

  • adding crushed stones or rocks to water, sand and cement makes concrete
  • concrete is a very strong stone-like material
  • pouring it over steel rods makes it stronger and is called reinforced concrete

C1A 2.1 EXTRACTING METALS

  • metals are

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