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

WJEC GCSE Additional Science Teacher’s Notes
PRACTICAL Making molecular models (page 106)
A unit cell is the smallest repeating unit in the structure of a giant structure.
sodium chloride
unit cell
diamond
unit cell
graphite unit cell
_ Carbon nanotubes (pages 106–107)______________
Questions
24. What are carbon nanotubes
Carbon nanotubes are another allotrope of carbon produced when graphite layers form and then
roll up into tubes rather than being deposited in layers.
25. Why are materials made from carbon nanotubes a good choice for components on a bike
Carbon nanotubes are incredibly strong, but very lightweight. This makes them ideal for use on
high performance bicycle components.
26. Why do carbon nanotubes conduct electricity How could they be made into electrical connections
inside electronic devices
Carbon nanotubes are good conductors of electricity due to the free electrons that can move up
and down the tubes. The tubes could be manufactured to behave like electrical wire
connections between electronic components on printed circuit boards – with very high
conductivities yet 10 000 times thinner than a human hair!
Discussion point
Carbon nanotubes are definitely a material for the future – can you think of any good applications for a very
lightweight, incredibly strong, electrically conducting material
Lots of military applications, portable computing, mobile phones, aerospace engineering, etc.
_Smart materials (pages 108–109)________________
Questions
27. What is a ‘smart material’
Smart materials have properties which change reversibly with a change in their surroundings.
28. Explain the difference between:
a a thermochromic pigment and a photochromic pigment
A thermochromic pigment changes colour with changing temperature, whereas a
photochromic pigment changes colour with changing light intensity.
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