Chemistry

• Filtration practical


  1. Grind mixture to make salt crystals smaller

  2. Put the mixture in water

  3. Sand won't dissolve, salt will

  4. Filter mixture to remove large particles of sand

  5. Evaporate the water from the salt to form dry crystals
• What happens when elements are mixed

  Different metals have different sized atoms. When another element is mixed with a pure metal, the new atoms will distort the layers of metal atoms, making it more difficult for them to slide over each other.
• Alloys


  • They are harder than pure metals
  • Pure metals aren't quite good for certain jobs, often because they are too soft
  • Alloys are made by mixing pure metals with other elements to make them harder
• Alloys


  2 or more different elements mixing together
• Alloys are composed of metals and another element
• Metals


  • The layers of atoms in a metal can slide over each other making metals malleable
  • This means they can be bent, hammered or rolled into flat sheets
• Metallic bonds


  Most compounds with metallic bonds have VERY high melting and boiling points
• Metals solid at room temperature

  The electrostatic forces between the metal atoms + sea of delocalised electrons are very strong and need lots of energy to be broken
• Metallic bonding


  1. Electrons in the outer shell are delocalised

  2. Strong forces of electrostatic attraction between the atoms and shared negative electrons

  3. These hold the atoms together in a regular structure
• Metals


  • Consist of a giant structure
• Metals


  • Delocalised electrons carry electrical and thermal charge (heat energy) through the whole structure
• Delocalised electrons


  Electrons that are free to move throughout the whole structure of the metal
• Ionic compounds


  • When melted or dissolved, ions are free to move and can carry electric charge
  • Dissolve easily in water
• Ions


  Charged particles that can move and carry electric charge
• Metals and ionic compounds

  • Have high boiling and melting points
  • Many strong bonds so a lot of energy is needed to break them
• Regular lattice structure


  • Closely packed
  • Very strong electrostatic forces of attraction between oppositely charged ions
• Ionic compounds


  Have a regular lattice structure (giant ionic lattice)
• National grid


  A giant system of cables and transformers that covers the UK and connects power stations to consumers
• National grid


  Transfers electrical power from power stations to anywhere else on the grid
• When people get up in the morning, come from school or work, when it starts to get dark or cold

  Increases the demand
• What are allotropes of carbon