Structure and Properties - C2

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  • Structure and Properties
    • Giant Ionic Structures
      • Solid at room temperature
      • Conduct electricity when molten or dissolved
        • ions that carry charge can move freely
      • High melting/boiling point
        • The ionic bonds need a lot of energy to break the bonds
    • Simple Molecules
      • Atoms within molecule held by strong covalent bond
      • Has no overall charge so do not conduct electricity or carry a charge
      • intermolecular forces between molecules are weak
        • Have a low melting/boiling point and a gas at room temp.
        • This is the attraction between molecules
        • Larger molecules like C6H14 have stronger IF.  so will be liquids at room temperature
      • For example: H2, Cl2
    • Giant Covalent Structures
      • Also called macromolecules
      • Atoms held together by strong covalent bonds
        • Also joined to several other atoms
      • Covalent bonds need a lot of energy to break
        • Very high melting and boiling point
      • Example - Diamond is made of carbon atoms covalently bonded to four other carbon atoms
        • This makes it very hard and transparent
        • 3D structure - like a prism
      • Example - Graphite (type of carbon) Covalently bonded to to three other atoms
        • 2D structure made up of layers
          • Carbon atoms slide so they can rub of (pencil lead)
        • One electron from each atom is delocalised and can therefore conduct electricity and heat
      • Fullerenes
        • Large molecules formed from hexagonal rings of carbon
          • Join to form cage-like shapes with different numbers of carbon atoms
        • Useful as:
          • Catalysts
          • drug delivery into body
          • Lubricants
    • Giant Metallic Structures
      • Made of layers
        • Layers slide over each other so object can bend or stretch
          • Useful for wires, rods and sheets
      • Different sized atoms in alloys mean the layers cant slide
        • Makes object harder
      • Metals have delocalised electrons in their atoms so they are good conductors of heat and electricity
    • Properties of Polymers
      • The properties of polymers depend on the monomers used to make them
      • Changing reaction conditions can aslo change the properties of the polymer that is produced
        • Whether it's high density or low density for example
          • High density has a higher softening temp and is harder than low density
      • Polymers have  different properties depending on the monomer it's made of
        • Polyethene softens at lower temps than ploypropene
      • Thermosoftening polymers (like polyethene) become soft when heated and hard when cool, this makes them good for moulds
        • Thermosetting polymers dont change shape when heated because strong covalent bonds cross-link between the polymer chains
        • Chains weak - intermolecular forces break when heated and bring molecules back together when cool
    • Nanoscience
      • The study of small particles sized 1 - 100 nanometres
      • Nano particles behave differently to the bulk materials they're made of
        • Their small size gives them a large surface area + new properties
      • More research needed into possible issues that might arise from increased use
      • Nanoparticles are used in nanotechnology
        • Selective sensors
        • Very efficient catalysts
        • new cosmetics like sun cream and deodrant
        • If used more could get into air and bodies
          • Could cause damage and so more research is being done


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