Chemistry C2.2: Structure and properties

HideShow resource information
  • Created by: Jordan64
  • Created on: 21-04-16 19:55
View mindmap
  • C2.2: Structure and properties
    • C2.5: The properties of polymers
      • The properties of a polymer depend on the monomers used to make it and the conditions we use to carry out the reaction.
        • Poly(propene) is made from propene and softens at a higher temperature than poly(ethane), which is made from ethene
          • Low density (LD) poly(ethane) and high density (HD) poly(ethane) are made using different catalysts and different reaction conditions.
            • HD poly(ethane) has a higher softening temperature and is stronger than LD poly(ethane)
          • Poly(ethane) is an example of a thermosoftening polymer.
            • It is made up of individual polymer chains that are tangled together.
              • When it is heated it becomes soft and hardens again when it cools.
                • This means that it can be heated to mould it into shape and it can be remoulded by heating it again.
            • Other polymers called thermosetting polymers do not melt or soften when we heat them.
              • These polymers set hard when they are first moulded because strong covalent bonds form cross-links between their polymer chains.
                • The strong bonds hold the polymer chains in position.
            • In thermosoftening polymers the forces between the polymer chains are weak
              • When we heat the polymer, these weak intermolecular forces are broken and the polymer becomes soft.
                • When the polymer cools down, the intermolecular forces bring the polymer molecules back together so the polymer hardens again.
    • C2.2: Simple molecules
    • C2.4: Giant covalent structures
      • Metal atoms are arranged in layers.
        • When a force is applied the layers of atoms can slide over each other.
        • They can move into a new position without being apart, so the metal bends or stretches into a new shape
        • Alloys are mixtures of metals or metals mixed with other elements.
          • The different sized atoms in the mixture distort the layers in the metal structure and make it more difficul for them to slide over eachother.
            • This makes alloys harder than pure metal
          • Shape memory alloys can be bent or deformed into different shape. When they are heated they return to their original shape.
            • They can be used in many ways, for example as dental braces.
        • Metal structures have delocalised electrons
          • Metals are good conductors of electricity because the delocalised electrons move throughout the giant metallic lattice and can transfer energy quickly
    • C2.1: Structure and bonding
      • Ionic compounds have giant structures in which many strong electrostatic forces hold the ions together.
        • A lot of energy is needed to overcome the ionic bonds to melt the solids
          • This means that they are solid at room temperature
          • Therefore, ionic compounds have high melting and boiling points
            • This means that they are solid at room temperature
        • However, when an ionic compound has been melted or dissolved, the ions are free to move.
          • This allows them to carry an electrical charge, so the liquids conduct electricity
          • Some ionic solids dissolve in water because water molecules can split up the lattice
            • This allows them to carry an electrical charge, so the liquids conduct electricity
        • It cannot conduct electricity because the ions can only vibrate around fixed positions - they cannot move around.
          • However, when an ionic compound has been melted or dissolved, the ions are free to move.
            • Some ionic solids dissolve in water because water molecules can split up the lattice
      • C2.6: Nanoscience
        • Nanoscience is the study of small particles that are between 1 and 100 nanometres in size.
          • When atoms are arranged into very small particles they behave differently to ordinary materials made of the same atoms.
          • A nanometre is one billionth of a metre (or 10 to the power of -9) and nanoparticles are a few nanometres in size.
          • Nanotechnology uses nanoparticles as highly selective sensors, very efficient catalysts, new coatings, new cosmetic such as sun screens and deodorants, and to give construction materials special purposes.
          • If nanoparticles are used more and more there will be a greater risk of them finding their way into the air and into our bodies
            • This could have unpredictable consequences for our health and the environment.
              • More research needs to be done about their health and effects.
                • If nanoparticles are used more and more there will be a greater risk of them finding their way into the air and into our bodies
                  • This could have unpredictable consequences for our health and the environment.
                    • More research needs to be done about their health and effects.
        • C2.3: Giant covalent structures

      Comments

      No comments have yet been made

      Similar Science resources:

      See all Science resources »See all Chemistry resources »