C2 : Structure and properties

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  • Created by: KAustria
  • Created on: 09-05-14 22:05
Why do giant ionic compounds have high melting and boiling points?
They have strong electrostatic forces which hold the ions together, which 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?
The ions are free to move and therefore able to carry an electric current. Water is able to break up the lattices.
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Why do simple molecule have low melting and boiling points?
the intermolecular forces between simple molecules can be simply overcome through boiling or melting.
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Can simple molecules carry an electric current?
No because molecules have no overall charge and so cannot carry an electric charge.
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What are forces of attraction called between molecules?
Intermolecular forces.
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Why are substances with large molecules more likely to be liquids or solids at room temperatures?
Larger molecules have stronger attractions and so may be liquids at room temperature.
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What are giant covalent bonds or macromolecular bonds?
Elements that can form several coavalent bonds and are able to join.
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Why do substances with giant colavlent structures have very high melting points?
Every atom in the structure is joined to several other atoms by strong covalent bonds, so it takes an enomous amount of energy to break down the lattice.
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Describe the structure of diamond
1. Form of Carbon 2. 3D giant structure 3. Every atom is covalently bonded to FOUR other covalent bonds
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Describe the structure of graphite
1. Form of carbon in which the atoms are covalently bonded to THREE other carbon atoms in giant flat 2D layers 2. No bonds between layers so they slide over each other.
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Why can graphite conduct electricity?
One electron from each carbon atom is delocalised which allow graphite to conduct heat and electricity.
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What are fullerenes?
Large molecules formed from hexagonal rings at carbon atoms.
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What are alloys?
A mixture of metals or metals mixed with other elements. The different sized atoms distort the layers in the metal structure and make it more difficult for them to slide over each other. This means they are harder than pure metal.
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What are shape memory alloys?
Alloys that can be bent or deformed into a different shape. When they are heated they return to their original shape.
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Why are metal structure good conductors of electricity and heat?
They have delocalised electrons which can move throughout the giant metallic lattice and transfer energy quickly.
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What is the difference between LD and HD poly(ethene) and why?
They are made with different catalysts and different reaction conditions. HD has a higher softening temperature than LD.
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What are thermosoftening polymers?
Made up of individual polymer chains that are tangled together. When it is heated it becomes soft and hardens again when it cools, which is a process which can be repeated.
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What are thermosetting polymers?
They do not melt or soften when they are heated,
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Why can't you remould thermosetting polymers?
Strong covalent bonds form cross-links between the polymer chain, which are held by the covalent bonds.
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What allow thermosoftening polymers to be remoulded?
1. Intermolecular forces are weak 2. When heated, intermolecular forces are broken and the polymer becomes soft. 3. When it cools down, the intermolecular forces bring the polymer molecules back together and it hardens
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What is nanoscience?
The study of small particles that are between 1 and 100 nanometres in size
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Other cards in this set

Card 2

Front

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

Back

The ions are free to move and therefore able to carry an electric current. Water is able to break up the lattices.

Card 3

Front

Why do simple molecule have low melting and boiling points?

Back

Preview of the front of card 3

Card 4

Front

Can simple molecules carry an electric current?

Back

Preview of the front of card 4

Card 5

Front

What are forces of attraction called between molecules?

Back

Preview of the front of card 5
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