Carbon nanotubes
Q1. This drill contains an electric motor.
The diagram below shows the main parts of an electric motor.
The carbon contacts are made of graphite. Springs push the contacts against the copper ring.
The carbon contacts conduct electricity to the copper ring. The copper ring rotates rapidly but
does not stick or become worn because the graphite is soft and slippery.
(a)
Using this information give two properties that make graphite suitable for making the
carbon contacts.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________ (2)
(b)
(i)
Draw a ring around the correct word in each box to complete the sentence.
Each carbon atom in graphite is joined to
two
three
four
covalent
other carbon atoms
by
ionic
bonds.
metallic
(2)
(ii)
Tick ( ) the statement which explains why graphite is soft and slippery.
Tick (
)
Statement
It is made of layers of atoms.
It is made of small molecules.
It is an ionic compound.
(1) (Total 5 marks)
Q2. Read the information
Graphene
Scientists have made a new substance called graphene.
The bonding and structure of graphene are similar to graphite.
Graphene is made of a single layer of the same atoms as graphite.
Graphene
Graphite
Use the information above and your knowledge of graphite to answer the questions.
(a)
This part of the question is about graphene. Choose the correct answer to complete each sentence.
(i)
ionic
covalent
metallic
The bonds between the atoms in graphene are _______________________
(ii)
chromium
carbon
chlorine
Graphene is made of __________________________ atoms.
(iii)
2
3
(1)
(1)
4
In graphene each atom bonds to ___________ other atoms.
(1)
(b)
This part of the question is about graphite.
Graphite is used in pencils.
Explain why. Use the diagrams to help you.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 5 marks)
Mark schemes
Q1.
(a)
any two from:
•
conducts electricity
•
soft
•
slippery
•
high melting point
ignore hardwearing / does not stick
apply list principle
2
(b)
(i)
three
1
covalent
1
(ii)
it is made of layers of atoms
1
[5]
Q2.
(a)
(i)
covalent
two different answers indicated gains 0 marks
1
(ii)
carbon
two different answers indicated gains 0 marks
1
(iii)
3
two different answers indicated gains 0 marks
1
(b)
layers can slide / slip
1
because there are no bonds between layers
accept because weak forces / bonds between layers
or so (pieces of) graphite rubs / breaks off
or graphite left on the paper
1
[5]
Q3.
Level 3 (5–6 marks):
A detailed and coherent explanation applying knowledge of the properties of nanotubes,
with
clear and logical links to reasons why carbon nanotubes have these properties
Level 2 (3–4 marks):
Description contains relevant statements that demonstrate clear knowledge of the
properties of nanotubes. Attempt made to link properties to explanation of why these
properties occur, but
logic may be unclear
Level 1 (1–2 marks):
Simple relevant statements of the properties of nanotubes, demonstrating knowledge,
but no linking to an explanation of why these properties occur.
0 marks:
No relevant content.
Indicative content
properties:
•
high tensile strength
•
high electrical / thermal conductivity
•
high melting point
explanations:
•
nanotubes are fullerenes based on hexagonal rings of carbon atoms
•
which means that each carbon forms three covalent bonds with three other
carbon atoms
•
covalent bonds are strong or need a lot of energy to break them
•
so nanotubes are strong / have high tensile strength
•
and have a high melting point
•
the structure means that one electron from each carbon atom is delocalised
•
as in metals and graphite, the delocalised electrons can move throughout the
structure
•
allowing the carbon nanotube / fullerene to conduct thermal energy and
electricity
[6]