Teacher's notes and answers to questions in the book - Hodder Plus ...

WJEC GCSE Additional Science Teacher’s Notes
10
Chemical bonding, structure
and properties
_Copper – a metal (pages 99–100)_________________
Questions
1. What are the two most important properties of metals
Metals are good conductors of heat and electricity.
2. What properties make copper such a good material for making water pipes
Copper is unreactive, malleable and ductile.
3. Why are electrical connecting wires made out of strands of copper
Strands of wire allow the connecting leads to be much more flexible.
4. Why are metals such good conductors of electricity
Metals have a ‘sea’ of negatively charged, free electrons that can easily move throughout the
structure of the metal.
5. Describe how the ‘positive ion/free electron’ model of copper can be used to explain its physical
properties:
a High melting and boiling point
The metallic bonds holding the positive metal ions together in their lattice structure are
very strong and need a lot of heat energy to break them.
b Ductility
Although metallic bonds are strong, copper has relatively weaker bonds than other metals
making it quite ductile – the bonds can be pulled apart during stretching.
c
Malleability
As (b) but the bonds can also be hammered or squashed into shape.
d Toughness
The fact that the copper metallic bonds allow themselves to be deformed out of shape
means that they will not fracture (break apart) easily when stressed.
Discussion point
Your teacher may show you an animation of conduction of electricity in a metal. How does the conductivity
of a metal change with temperature, the dimensions of the wire and the material that the wire is made of
An excellent animation to use, if you can get hold of a copy of it, is ‘Resistance Simulator’ by
Vibrant Effects Ltd.
On-line alternatives are:
www.absorblearning.com/media/item.actionquick=t6
www.absorblearning.com/media/item.actionquick=11a
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