C2.2

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Explain why alloys are harder than pure metal and how they can be used.
Metals atoms are arranged in layers making them soft and therefore malleable and ductile. Alloys are mixtures of metals and the different sized atoms distort the layers and make it more difficult for the layers to slide over each other. Shape memory
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Describe the structure and bonding in a thermosoftening polymer and explain why thermosoftening polymers melt when heated.
Thermosoftening polymers consist of tangled polymer chains with weak intermolecular forces which mean that the polymers melt when heated and harden when they cool. Thermosetting polymers set hard when first moulded because strong covalent bonds form
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Explain why, in terms of structure, carbon dioxide is a gas, even at low temperatures.
Carbon has weak intermolecular forces and is made of small molecule and therefore has a low melting and boiling point. Therefore Carbon dioxide is a gas a room temperature and low temperatures.
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Why do ionic solids have high melting & boiling points?
They have a giant structures in which many strong electrostatic forces hold the ions together. This means that they are solids at room temperature. A lot of energy is needed to overcome the ionic bonds to melt the solids.
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Why can ionic substances conduct electricity when molten or when dissolved in water?
When an ionic compound has been melted the ions are free to move. This allows them to carry electrical charge, so the liquids conduct electricity. Some ionic solids dissolve in water because the water molecules split up the lattice and the ions are f
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What are the properties of simple molecules?
Strong covalent bonds between atoms within molecule = weak intermolecular forces (overcome when melted/boiled) = low melting/boiling points. Molecules have no overall charge = can’t carry electrical charge.
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What are giant covalent bonds?
Substances with high melting points due to the strong covalent bonds forming a lattice that requires enormous amounts of energy to break down
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Give two similarities and differences between diamond and graphite?
Both carbon and covalent bonds. Diamond = 1 carbon atom + 4 other Carbon atoms = strong & hard. Graphite = 1 carb atom + 3 carb atoms (one of which delocalised) forming flat sheet of hexagons = giant 2D layers
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Explain the structure of graphite and its consequences?
Graphite = 1 carb atom + 3 carb atoms (one of which delocalised) forming flat sheet of hexagons = giant 2D layers. No covalent bonds between layers & so slide over each other = slippery + grey. Delocalised electrons = g conducts heat + electricity.
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Why can metals be made into wires?
Atoms arranged in layers that can slide over each other & move into a new shape without breaking.
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What are fullerenes?
Large molecules formed from hexagonal rings of carbon atoms which join together to form cage-like shapes with different number of carbon atoms some of which = nano-sized. Uses = drug delivery into body, lubricants, catalysts, + reinforcing materials.
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Why are metals good conductors of electricity?
The delocalised electrons move throughout the giant metallic lattice &so can transfer energy quickly
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Why do LD and HD poly(ethene) have different properties?
Made using different reaction conditions; different structures + differently shaped molecules.
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What is a nanoparticle?
Particle a few nanometres in size made of a few hundred atoms with large surface areas& small sizes = new properties as they behave differently to normal materials.
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What can nanotechnology be used for and what needs to be done before it is?
Used for efficient catalysts, new coatings & cosmetics (sunscreen + deodorants) but may have unpredictable consequences for health and the environment. Need more research on effects.
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Card 2

Front

Describe the structure and bonding in a thermosoftening polymer and explain why thermosoftening polymers melt when heated.

Back

Thermosoftening polymers consist of tangled polymer chains with weak intermolecular forces which mean that the polymers melt when heated and harden when they cool. Thermosetting polymers set hard when first moulded because strong covalent bonds form

Card 3

Front

Explain why, in terms of structure, carbon dioxide is a gas, even at low temperatures.

Back

Preview of the front of card 3

Card 4

Front

Why do ionic solids have high melting & boiling points?

Back

Preview of the front of card 4

Card 5

Front

Why can ionic substances conduct electricity when molten or when dissolved in water?

Back

Preview of the front of card 5
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