Giant Covalent Structures
1
Do not write
outside the
box
The diagram shows some bricks that are used to line the inside of a furnace. The
bricks contain silicon dioxide. The structure of silicon dioxide is shown below.
Silicon dioxide
1 (a) (i)
Bricks containing silicon dioxide
Describe the structure and bonding in silicon dioxide and explain why it is a suitable for
making bricks for the inside of a furnace.
Structure marks (max 3)
• Giant structure / macromolecule / all the atoms are joined together
• Covalent (bonds)
• Strong bonds / bonds difficult to break
• Each silicon atom forms 4 bonds and / or each oxygen atom forms 2 bonds
Explanation marks (max 3)
• A lot of energy needed to break the bonds
• High melting point
• Does not burn or react with oxygen
This would be a similar to why diamond has a high
melting point. Make sure you are familiar with the
structure of diamond and silicon dioxide. See the
video if you are not sure.
(5 marks)
The questions continue on the next page
Total (5 marks)
my-­‐GCSEscience.com ESPQ|PHY2|GNCOS Giant Covalent Structures
2
The element carbon comes in different forms. The structures of two forms of carbon,
graphite and diamond, are shown below.
Although they are both forms of carbon, graphite and diamond have different properties.
Diamond
2 (a) (i)
Graphite
Diamond is much harder than graphite. Graphite can conduct electricity but diamond
cannot.
Explain why.
Because layers of carbon atoms in graphite can either move or slide [1 mark]
This is because there are only weak intermolecular forces or weak forces between the
layers [1 mark]
Diamond: in diamond each carbon atom is strongly (covalently) bonded to 4 others
[1 mark]
So no carbon atoms are able to move or slide [1 mark]
Graphite: graphite has delocalised or free electrons or a sea of electrons [1 mark]
Which can carry current would charge through the structure [1 mark]
Diamond has no delocalised electrons [1 mark]
You can say that all of the electrons in the outer shell are
used in bonding. The exam board is fussy about you
saying that the electrons can move through the structure,
that’s why it is underlined in the answers above.
(6 marks)
(Total 6 marks)
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