AQA GCSE Chemistry Chemistry Paper 1 (Higher), November 2020: Question 1

8 marks · Standard Demand difficulty · Extended Answer

Identify substances with intermolecular forces and compare the structure and bonding of carbon dioxide, magnesium oxide, and silicon dioxide.

Practise this question

Question

Question text

01 This question is about structure and bonding.

01.1 Which two substances have intermolecular forces between particles?

[2 marks]

Tick ( ) two boxes.

Diamond

Magnesium

Poly(ethene)

Sodium chloride

Water

01.2 Table 1 shows the structures of three compounds.

Table 1 Diagrams not to scale

Compound Structure

Carbon dioxide

Magnesium oxide

Silicon dioxide

Compare the structure and bonding of the three compounds:

• carbon dioxide

• magnesium oxide

*02* • silicon dioxide.

[6 marks]

Mark scheme

Show the mark scheme

Question 1

AO /

Question Answers Extra information Mark

Spec. Ref.

01.1 poly(ethene) 1 AO2

4.2.1.4

water 1 4.2.2.4

4.2.2.5

Question 1 continued

AO/

Question Answers Mark

Spec. Ref

01.2 Level 2: Scientifically relevant features are identified; the way(s) in 4–6 AO1

which they are similar/different is made clear and (where 4.2.1.2

appropriate) the magnitude of the similarity/difference is noted. 4.2.1.3

4.2.1.4

Level 1: Relevant features are identified and differences noted. 1–3

No relevant content 0

Indicative content

• (both) carbon dioxide and silicon dioxide are made up of atoms

• (but) magnesium oxide is made up of ions

• (both) silicon dioxide and magnesium oxide are giant structures

• (but) carbon dioxide is small molecules

• with weak intermolecular forces

• all three compounds have strong bonds

• (both) carbon dioxide and silicon dioxide are formed from two

non-metals

• (so) bonds formed are covalent

• (so) electron (pairs) are shared (between atoms)

• (but) magnesium oxide is formed from a metal and a non-metal

• (so) bonds in magnesium oxide are ionic

• (so) electrons are transferred

• from magnesium to oxygen

• two electrons are transferred

• bonds in silicon dioxide are single bonds

• (where) each silicon forms four bonds

• (and) each oxygen forms two bonds

7 • (but) in carbon dioxide the bonds are double bonds

• (where) carbon forms two double bonds

• (and) oxygen forms one double bond

ignore properties e.g. melting point, electrical conductivity

Total 8

How to answer it

Structure and Bonding: Comparing Types of Substances

What this question tests

This question assesses your understanding of chemical bonding and structural types: identifying substances with intermolecular forces (small molecules and polymers) and conducting a detailed, comparative analysis of structure (giant vs simple, particles present) and bonding (ionic vs covalent, electron sharing vs electron transfer) across three distinct chemical substances: CO₂, MgO, and SiO₂.

Question 01.1 • 2 Marks

Identifying Substances with Intermolecular Forces

Tick (✓) two boxes

✅ Correct Answers

Poly(ethene) [1 mark]
Water [1 mark]

💡 Key Knowledge

Intermolecular forces exist exclusively between molecules. They are found in:

Small covalent molecules (e.g. water, H₂O; carbon dioxide, CO₂)
Polymers (e.g. poly(ethene)), which are very large covalent molecules held together by many intermolecular forces.

❌ Common Errors & Misconceptions

Ticking Diamond: Diamond is a giant covalent structure made of strong covalent bonds throughout; it contains no separate molecules, so no intermolecular forces exist.
Ticking Sodium chloride or Magnesium: Sodium chloride has ionic bonds throughout an ionic lattice; magnesium has metallic bonds throughout a metallic lattice. Neither has molecules.
Confusing polymer bonds: Believing polymers only have covalent bonds. While the polymer backbone is covalent, polymer chains are held to adjacent chains by intermolecular forces.

🧠 Exam Technique

Whenever a question asks for intermolecular forces, immediately translate that to: "Which of these substances are molecular?" Eliminate giant lattices (ionic, metallic, giant covalent) first.

Marking rule: Exactly 2 marks available. If a student ticks more than two boxes, marks are deducted for incorrect extra ticks.

Question 01.2 • 6 Marks (Extended Response)

Comparing Structure and Bonding: CO₂, MgO, and SiO₂

Use information from the diagrams and your chemistry knowledge

📐 Direct Side-by-Side Comparison

Feature	Carbon dioxide (CO₂)	Magnesium oxide (MgO)	Silicon dioxide (SiO₂)
Type of Structure	Simple molecular (small molecules)	Giant ionic lattice	Giant covalent lattice
Constituent Particles	Non-metal atoms forming molecules	Oppositely charged ions (Mg²⁺ and O²⁻)	Non-metal atoms (Si and O)
Type of Bonding	Covalent (shared electron pairs)	Ionic (electrostatic attraction between ions)	Covalent (shared electron pairs)
How Bonds Form	Sharing electrons; double bonds (C forms 2 double bonds, O forms 1)	Transfer of 2 electrons from Mg to O	Sharing electrons; single bonds (Si forms 4 bonds, O forms 2)
Forces Holding Structure	Weak intermolecular forces between molecules	Strong electrostatic attraction between ions throughout	Strong covalent bonds throughout the giant network

✅ Model Structure for a Level 2 (5–6 Mark) Answer

1. Comparison of Structure:

Both MgO and SiO₂ are giant structures / giant lattices, whereas CO₂ consists of small / simple molecules with weak intermolecular forces between them.
Both CO₂ and SiO₂ consist of atoms, whereas MgO consists of ions (Mg²⁺ and O²⁻).

2. Comparison of Bonding:

All three compounds contain strong chemical bonds.
CO₂ and SiO₂ both contain covalent bonds because they are formed between non-metals, meaning pairs of electrons are shared.
In contrast, MgO contains ionic bonds because it is formed from a metal and a non-metal, where two electrons are transferred from magnesium to oxygen.
Bond details (for top marks): In SiO₂, atoms are linked by single covalent bonds (each Si forms 4 bonds, each O forms 2 bonds). In CO₂, there are double covalent bonds (carbon forms two double bonds).

❌ Crucial Examiner Warning

"Ignore properties e.g. melting point, electrical conductivity."

A very common trap in this question is writing paragraphs about high/low melting points, boiling points, or conduction of electricity. The question explicitly asks for structure and bonding only. Mentioning properties scores zero marks!

🧠 How to Secure Full 6 Marks

Spot similarities AND differences: Don't just describe each substance separately. Group them together (e.g. "Both SiO₂ and MgO are giant, whereas CO₂ is simple molecular...").
Mention all 3 substances: Failing to address all three limits you to Level 1 (max 3 marks).
Cover both aspects: Make sure you have clearly distinguished structure (how particles are arranged) from bonding (the forces / electron interactions between particles).

Level 2 (4–6 marks): Scientifically relevant features identified; similarities and differences clearly structured and compared.

Topics

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

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