Question 1 Medium
State why methane has a low boiling point.
Show answer
Answer: weak intermolecular forces
- Methane is a simple molecule.
- It has weak intermolecular forces.
Covalent bonding and giant covalent structures: GCSE Combined Science Chemistry practice questions
A second set of questions on covalent bonding and giant covalent structures. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
More questions
Question 2 Medium
How many carbon atoms are in one molecule of buckminsterfullerene?
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Answer: 60
- Its formula is C₆₀.
- So it has 60 carbon atoms.
Question 3 Medium
How many covalent bonds does each carbon atom form in graphite?
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Answer: 3
- Each carbon is bonded within a layer.
- It joins to three other carbon atoms.
Question 4 Medium
Name the compound that is the main substance in sand.
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Answer: silicon dioxide
- It contains silicon and oxygen.
- The formula is SiO₂.
Question 5 Hard
Explain why diamond has a very high melting point.
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Answer: it has many strong covalent bonds that need a lot of energy to break
- Each carbon forms four strong covalent bonds.
- A lot of energy is needed to break so many bonds.
Question 6 Hard
Explain why graphene is a good conductor of electricity.
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Answer: it has delocalised electrons
- Each carbon bonds to three others.
- The fourth outer electron is delocalised and can carry charge.
Question 7 Hard
Silicon dioxide does not conduct electricity. Give a reason.
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Answer: it has no free electrons or ions
- All the outer electrons of each atom are in bonds.
- There are no delocalised electrons or ions.
Question 8 Hard
Explain why polymers have higher melting points than small molecules such as ethene.
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Answer: the intermolecular forces between the long chains are stronger
- Polymer molecules are very large.
- The intermolecular forces are stronger so more energy is needed.
Question 9 Hard
Which kind of model shows the bonds and the shape of a molecule but uses sticks that are not real?
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Answer: ball and stick
- The balls are atoms.
- The sticks represent bonds, but they are not real.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is a covalent bond?
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A shared pair of electrons between two atoms.
Check 2
Between which types of atoms do covalent bonds form?
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Non-metal atoms.
Check 3
Are covalent bonds strong or weak?
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Strong.
Check 4
What is overcome when a simple molecular substance melts?
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The weak intermolecular forces.
Check 5
Why do larger molecules have higher boiling points?
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The intermolecular forces are stronger.
Check 6
Why do simple molecules not conduct electricity?
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They have no free electrons or ions.
Check 7
How many bonds does each carbon atom form in diamond?
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Four.
Check 8
How many bonds does each carbon atom form in graphite?
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Three.
Check 9
Why can graphite conduct electricity?
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It has delocalised electrons.
Check 10
Why is graphite soft and slippery?
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The layers are held by weak forces and slide over each other.
Check 11
What is silicon dioxide?
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The main compound in sand, with a giant covalent structure.
Check 12
What is graphene?
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A single layer of graphite, one atom thick.
Check 13
What is the formula of buckminsterfullerene?
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C₆₀.
Check 14
Name one use of carbon nanotubes.
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Strengthening materials, or as catalysts, or in electronics.
Check 15
What does delocalised mean?
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Not attached to one atom and free to move.
Check 16
Why are polymers solid at room temperature?
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The intermolecular forces between the long chains are strong enough.
Check 17
What are intermolecular forces?
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The weak forces between molecules.
Check 18
What is a giant covalent structure?
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A huge network of atoms joined by strong covalent bonds.
Check 19
How many bonds does an oxygen atom form in water?
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Two.
Check 20
How many bonds does a carbon atom form in methane?
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Four.
Check 21
Why does diamond not conduct electricity?
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It has no free electrons or ions.
Check 22
What is diamond used for?
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Cutting tools.
Check 23
What is graphite used for?
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Lubricants, pencils and electrodes.
Check 24
How many oxygen atoms is each silicon atom bonded to in silicon dioxide?
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Four.
Check 25
What shape are the rings in a layer of graphite?
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Hexagons.
Check 26
What is a carbon nanotube?
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A cylinder made of carbon atoms.
Check 27
What does a dot and cross diagram show?
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The outer electrons of each atom, and the shared pairs in a covalent bond.
Check 28
What is a limitation of a dot and cross diagram?
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It does not show the shape of the molecule or the size of the atoms.
Check 29
What is a limitation of a ball and stick model?
Show answer
The sticks are not real, and it does not show the real size of atoms or the space between them.
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