Structure and properties

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  • Created by: Sam Evans
  • Created on: 01-01-15 22:42
Why does it take a lot of energy to melt sodium chloride?
It has a giant ionic structure with strong electrostatic forces/bonds that hold the ions firmly in position and that need a lot of energy to overcome/break them
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Why are compounds like methane, CH4, and ammonia, NH3, gases at room temperature?
They are made of small molecules or covalent bonds act only between the atoms within a molecule
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Polymers made from different monomers have different properties. Explain why.
Different monomers change the structure of the polymer chains or the polymer chains have different shapes/structures
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Some dental braces are made from shape-memory alloys. What is meant by a 'shape-memory alloy'?
An alloy (mixture of metals) that can be bent/deformed and changes back to its original shape when heated
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Explain why diamonds are very hard.
Every carbon atom is covalently/strongly bonded to four other carbon atoms in a giant (3-D) covalent structure
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Why do ionic compounds need to be molten or in solution to conduct electricity?
The ions cannot move in the solid, but become free to move in the molten liquid or in solution.
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Explain why a block of copper can be hammered into a sheet.
The atoms are in layers. The layers slide over each other, into the new shape, without breaking apart
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How are silver nanoparticles different from ordinary silver particles?
They are very much smaller, have a much greater surface area
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Suggest why a sock manufacturer would use nanoparticles instead of ordinary silver particles.
They are more effective (because of their greater surface area), needs to use much less silver (so it is cheaper), easier to attract to sock fibres.
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Explain why thermosetting polymers are often used to make handles for cooking pans.
They do not soften/melt when they get hot, they are good insulators (of heat) they can be moulded into shape but then are rigid/hard
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Explain how the atoms in a metal are bonded to each other
The outer electrons delocalise, leaving a lattice of positive ions: the delocalised electrons strongly attract the positive ions and hold them in position
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Why can graphite conduct electricity?
There are delocalised electrons in graphite or one electron from each carbon atom is delocalised: the delocalised electrons carry the electrical charge
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Explain what is meant by 'intermolecular forces'.
Forces between molecules (that are much weaker than covalent bonds within the molecules)
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C60 is a fullerene. What are fullerenes?
Forms of carbon, with large molecules, based on hexagonal rings of carbon atoms, often cage-like structures, can be nano-sized, have many useful applications
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Other cards in this set

Card 2

Front

Why are compounds like methane, CH4, and ammonia, NH3, gases at room temperature?

Back

They are made of small molecules or covalent bonds act only between the atoms within a molecule

Card 3

Front

Polymers made from different monomers have different properties. Explain why.

Back

Preview of the front of card 3

Card 4

Front

Some dental braces are made from shape-memory alloys. What is meant by a 'shape-memory alloy'?

Back

Preview of the front of card 4

Card 5

Front

Explain why diamonds are very hard.

Back

Preview of the front of card 5
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