AQA GCSE Combined Science: Trilogy Chemistry Paper 1 (Foundation), 2020: Question 7

8 marks · Standard Demand difficulty · Short Answer

Answer questions on covalent bonding, intermolecular forces, the molecular formula of a displayed molecule, and the structure and properties of diamond and other giant covalent substances.

Practise this question

Question

An exam page section titled 'This question is about substances with covalent bonding' contains six short questions labelled 07.1 to 07.6. Question 07.1 shows a simple ball-and-stick diagram of a water molecule, H2O, and asks for one limitation of using a ball and stick model for water, worth 1 mark. Question 07.2 states 'Ice has a low melting point' and asks to complete the sentence explaining that the intermolecular forces are blank, worth 1 mark. Question 07.3 shows a photo of a ball-and-stick model with labels for oxygen atom, hydrogen atom, and carbon atom, asking for the molecular formula of the molecule in Figure 13, worth 1 mark. Question 07.4 states that diamond has a giant covalent structure and asks for the number of bonds formed by each carbon atom in diamond, with tick-box options 2, 3, 4, and 8, worth 1 mark. Question 07.5 asks for two physical properties of diamond, worth 2 marks. Question 07.6 asks to name two other substances with giant covalent structures, worth 2 marks.
Question text

07 This question is about substances with covalent bonding.

07.1 Figure 12 shows a ball and stick model of a water molecule (H2O).

Figure 12

Suggest one limitation of using a ball and stick model for a water molecule.

[1 mark]

07.2 Ice has a low melting point.

Water molecules in ice are held together by intermolecular forces.

Complete the sentence.

[1 mark]

Ice has a low melting point because the

intermolecular forces are 23 .

07.3 Figure 13 shows the structure of a molecule.

Figure 13

*22* What is the molecular formula of the molecule in Figure 13?

[1 mark]

Diamond has a giant covalent structure.

07.4 What is the number of bonds formed by each carbon atom in diamond?

[1 mark]

Tick ( ) one box.

23 4 8

07.5 Give two physical properties of diamond.

[2 marks]

07.6 Name two other substances with giant covalent structures.

[2 marks]

Mark scheme

Show the mark scheme The mark scheme lists answers for questions 07.1 to 07.6 in a table with columns for question, answers, extra information, marks, and AO/spec reference. For 07.1 acceptable limitations include not to scale, not 3 dimensional, incorrect arrangement in space, or electrons/shells not shown. For 07.2 the answer is weak or weaker. For 07.3 the answer is CH4O, with CH3OH allowed. For 07.4 the answer is 4. For 07.5 any two of hard, very hard, very high melting point, does not conduct electricity, or high thermal conductivity. For 07.6 acceptable examples include graphite, silicon dioxide/silica, silicon, polymers, fullerene, or carbon nanotubes, with buckminsterfullerene ignored.

AO /

Question Answers Extra information Mark

Spec. Ref.

07.1 any one from: 1 AO2

5.2.1.4

• not to scale allow size of atoms incorrect

• not 3 dimensional / D

• incorrect arrangement in allow atoms are separated

space

• electrons / shells not shown

ignore properties of water

07.2 weak allow weaker 1 AO1

5.2.2.4

07.3 CH4O allow CH3OH 1 AO2

5.2.1.4

07.4 4 1 AO1

5.2.3.1

07.5 any two from: 2 AO1

5.2.3.1

• (very) hard allow strong

• (very) high melting point

• does not conduct electricity

allow high thermal conductivity

ignore shiny

07.6 graphite allow graphene 1 AO1

5.2.2.6

silicon dioxide allow silica 1

allow silicon

allow polymer(s)

or allow (named) polymer(s)

allow fullerene

or allow carbon nanotubes

ignore buckminsterfullerene

Total 8

How to answer it

Covalent Bonding & Giant Structures

What this question tests

This question assesses your understanding of covalent bonding models, the nature of intermolecular forces, and the physical properties of giant covalent structures like diamond. You need to distinguish between simple molecular substances and giant covalent lattices.

Part 07.1: Limitations of Models

✅ Correct Answer

Any one of the following: Not to scale, not 3D, incorrect arrangement in space, or electrons/shells not shown.

💡 Key Knowledge

Models are simplifications. Ball and stick models show how atoms are connected, but they fail to represent the actual relative sizes of atoms or the true 3D geometry of the molecule.

Part 07.2: Intermolecular Forces

✅ Correct Answer

The intermolecular forces are weak.

🧠 Exam Technique

Always link melting/boiling points of simple molecules to the weak intermolecular forces. Do not say "covalent bonds are weak"—the covalent bonds within the molecule are very strong; it is the forces between the molecules that are weak.

Part 07.3: Molecular Formula

✅ Correct Answer

CH₄O (or CH₃OH )

❌ Common Errors

Counting atoms incorrectly. Ensure you count every sphere shown in the diagram. There is 1 Carbon, 4 Hydrogens, and 1 Oxygen.

Part 07.4: Bonding in Diamond

✅ Correct Answer

4

💡 Key Knowledge

In diamond, each carbon atom forms four strong covalent bonds with four other carbon atoms, creating a rigid, tetrahedral giant lattice.

Part 07.5: Properties of Diamond

✅ Correct Answer

Any two of: (Very) hard, (very) high melting point, does not conduct electricity.

🧠 Exam Technique

When asked for physical properties, avoid vague terms like "strong." Use specific scientific terminology like "high melting point" or "hard."

Part 07.6: Giant Covalent Structures

✅ Correct Answer

Graphite and Silicon Dioxide (Silica).

💡 Key Knowledge

Remember the "Big Three" of giant covalent structures: Diamond, Graphite, and Silicon Dioxide. These are all held together by a network of strong covalent bonds throughout the entire structure.

Topics

Chemistry · C2: Bonding, Structure and the Properties of Matter

Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Chemistry Paper 1 (Foundation), 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.