CH2 - Solid Structures
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- Created on: 22-03-16 21:24
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- CH2 - Solid Structures
- Giant Ionic Lattices
- Number of 'nearest neighbours' is the co-ordination number.
- Caesium Chloride, Cs+Cl-
- Cs+ ion is larger than the Cl- ion, so more Cl- ions can fit around each Cs+ ion.
- Cl- co-ordination number = 8
- Cs+ co-ordination number = 8.
- Crystal co-ordination number = 8:8 ratio.
- Caesium Chloride, Cs+Cl-
- Properties of Ionic Compounds
- High melting and boiling points.
- Strong ionic bonds (electrostatic attractions between oppositely charged ions).
- Large amount of heat energy is needed to break them.
- Strong ionic bonds (electrostatic attractions between oppositely charged ions).
- Water Soluble
- Positively charged metal ions form strong attractions with the polar O of the water.
- Negatively charged non-metal ions form strong attractions with the polar H of water.
- The attractions overcome the hydrogen bonds between the water molecules and therefore the compound dissolves.
- Conducting electricity when molten or aqueous.
- Ions are not free to move in the solid state.
- Melting or dissolving in water overcomes the ionic bonds.
- The ions become free to move and therefore carry a charge.
- High melting and boiling points.
- Number of 'nearest neighbours' is the co-ordination number.
- Giant Covalent Substances
- Diamond
- Clear
- Lustre
- No intermolecular forces.
- Graphite
- Opaque
- Black
- Hexagonal layers.
- Layered on top of one another.
- Weak intermolecular forces between each layer of graphite.
- Opaque
- Diamond
- Simple Covalent Substances
- Iodine
- Crystalline (solid) at room temperature.
- Gentle warming causes it to undergo sublimation.
- Changes state from a solid to a gas without melting first.
- NH3
- CH4
- Iodine
- Smart Materials
- Shape Memory Polymers
- Softens when heated, so can be softened or deformed.
- Remains in changed state when cooled.
- When reheated, original shape is 'remembered'.
- Shape Retention.
- E.G. Medical Sutures.
- Thermochromic Pigments
- Change colour (reversibly) when temperature changes.
- E.G. T-Shirts or Mugs
- Shape Memory Alloys
- Pseudo-elasticity (appear to be plastic).
- Exhibit shape retention memory.
- E.G. Deformable glasses frames.
- E.G. Surgical plates for joining surgical fractures.
- E.G. Thermostats for electrical devices.
- Photochromic Pigments
- Contain molecules that change colour when exposed to light.
- Particularly UV light.
- Light breaks a bond in the molecule so that it rearranges itself into a molecule with a different colour.
- E.G. Lenses of sunglasses.
- Original colour returns when the light source is removed.
- Contain molecules that change colour when exposed to light.
- Hydrogels
- Cross-linked polymers that have the ability to absorb or expel water when subjected to certain stimuli.
- E.G. Temperature or pH.
- E.G. Nappies or Artificial Muscles.
- Cross-linked polymers that have the ability to absorb or expel water when subjected to certain stimuli.
- Shape Memory Polymers
- Nano Materials
- Other Forms of Carbon
- Carbon Nano Tubes
- Single layer of graphite rolled into a tube.
- Fullerene type arrangement where the ends of the tubes are closed.
- 10,000 times thinner than a human hair.
- Extremely strong.
- May have the same adverse properties as asbestos fibres.
- Carbon Nano Tubes
- Nano Particles
- Range size from 1nm to 100 nm.
- 1nm = 0.000000001m
- When materials are made Nano-sized they have significantly different properties to the material in bulk.
- Drawback - Is there enough known about Nano-particles before they can be widely used.
- Could they be a risk to environmental health?
- E.G Nano-particles in the water supply.
- E.G If Nano-particles passed through our skin and have adverse biological effects?
- Could they be a risk to environmental health?
- Nanoparticles of Silver
- Anti-bacterial
- Wound/burn dressings.
- Anti-viral
- Sterilising sprays for operating theatres.
- Anti-fungal
- Interior surfaces of fridges.
- Anti-bacterial
- Range size from 1nm to 100 nm.
- Other Forms of Carbon
- Metallic Lattices
- Metals can be described as "an array of positive ions in a sea of delocalised electrons".
- Attraction of positive ions for the delocalised electrons is the metallic bond.
- Metallic bonds are generally strong.
- This is why metals have generally high melting and boiling points.
- E.G. Magnesium (Group 2 metal)
- The electrostatic attraction is 2+.
- Therefore the electrostatic attraction is greater than the electrostatic attraction of group 1 metals.
- Therefore group 2 metals have higher melting and boiling points than group 1 metals.
- The electrostatic attraction is 2+.
- Metallic bonds are generally strong.
- Attraction of positive ions for the delocalised electrons is the metallic bond.
- Metals can be described as "an array of positive ions in a sea of delocalised electrons".
- Giant Ionic Lattices
- Sodium Chloride, NA+Cl-
- Na+ co-ordination number = 6
- Number of 'nearest neighbours' is the co-ordination number.
- Caesium Chloride, Cs+Cl-
- Cs+ ion is larger than the Cl- ion, so more Cl- ions can fit around each Cs+ ion.
- Cl- co-ordination number = 8
- Cs+ co-ordination number = 8.
- Crystal co-ordination number = 8:8 ratio.
- Caesium Chloride, Cs+Cl-
- Cl- co-ordination number = 6
- Crystal co-ordination number = 6:6 ratio.
- Tetrahedral shape atoms.
- 3D lattice.
- Diamond
- Clear
- Lustre
- No intermolecular forces.
- Each carbon atom is connected to another carbon atom.
- Extremely hard to break apart.
- It is a volatile substance.
- It vaporises easily.
- Iodine
- Crystalline (solid) at room temperature.
- Gentle warming causes it to undergo sublimation.
- Changes state from a solid to a gas without melting first.
- Conduct electricity
- Makes them suitable as connectors in micro electronic circuits.
- Carbon Nano Tubes
- Single layer of graphite rolled into a tube.
- Fullerene type arrangement where the ends of the tubes are closed.
- 10,000 times thinner than a human hair.
- Extremely strong.
- May have the same adverse properties as asbestos fibres.
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