Chemistry C2.2: Structure and properties
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- Created on: 21-04-16 19:55
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- 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.
- When it is heated it becomes soft and hardens again when it cools.
- 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.
- These polymers set hard when they are first moulded because strong covalent bonds form cross-links between their polymer chains.
- 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.
- When we heat the polymer, these weak intermolecular forces are broken and the polymer becomes soft.
- It is made up of individual polymer chains that are tangled together.
- Low density (LD) poly(ethane) and high density (HD) poly(ethane) are made using different catalysts and different reaction conditions.
- Poly(propene) is made from propene and softens at a higher temperature than poly(ethane), which is made from ethene
- The properties of a polymer depend on the monomers used to make it and the conditions we use to carry out the reaction.
- 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.
- 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.
- 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
- Metal atoms are arranged in layers.
- 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
- Some ionic solids dissolve in water because water molecules can split up the lattice
- However, when an ionic compound has been melted or dissolved, the ions are free to move.
- A lot of energy is needed to overcome the ionic bonds to melt the solids
- Ionic compounds have giant structures in which many strong electrostatic forces hold the ions together.
- 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.
- More research needs to be done about their health and effects.
- This could have unpredictable consequences for our health and the environment.
- 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
- More research needs to be done about their health and effects.
- This could have unpredictable consequences for our health and the environment.
- Nanoscience is the study of small particles that are between 1 and 100 nanometres in size.
- C2.3: Giant covalent structures
- C2.5: The properties of polymers
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