AQA GCSE Chemistry Chemistry Paper 1 (Higher), June 2025: Question 5
12 marks · Standard Demand difficulty · Short Answer
Describe models of atomic structure and calculate the surface area to volume ratio of a cubic nanoparticle.
Practise this questionQuestion
Question text
05 This question is about small particles.
Before the discovery of the electron, atoms were thought to be tiny spheres that could
not be divided.
05.1 The discovery of the electron led to the plum pudding model of the atom.
Describe the plum pudding model of the atom.
[2 marks]
05.2 The model of the atom changed again after the alpha particle scattering experiment.
Give two conclusions that were made from the alpha particle scattering experiment.
[2 marks]
05.3 Niels Bohr made another change to the model of the atom.
What was this change?
[1 mark]
05.4 A helium atom has a radius of 1.4 × 10–10 m.
The nucleus of this atom has a radius of 1.7 × 10–15 m.
How many times larger is the radius of the atom than the radius of the nucleus?
[1 mark]
Tick ( ) one box.
∼1000 times larger
∼10 000 times larger
∼100 000 times larger
∼1 000 000 times larger 17
Nanoparticles contain a few hundred atoms.
05.5 Figure 5 represents a cubic nanoparticle.
Figure 5
Calculate the simplest surface area : volume ratio of the cubic nanoparticle.
[4 marks]
Simplest surface area to volume ratio = :
05 *.616Lenses in reading glasses often have a scratch-resistant coating that contains a*
hard substance.
Nanoparticles of the hard substance are used instead of fine particles of the
hard substance.
Explain why nanoparticles are used instead of fine particles.
[2 marks]
Mark scheme
Show the mark scheme
Question 5
AO /
Question Answers Extra information Mark
Spec. Ref.
05.1 a ball of positive charge allow a positive(ly charged) ball 1 AO1
4.1.1.3
do not accept references to
protons, nuclei, neutrons
with (negative) electrons 1
embedded
AO /
Spec. Ref.
05.2 any two from: 2 AO1
4.1.1.3
• the mass of the atom is
concentrated at the centre /
nucleus
• the nucleus is positive /
charged
• most of the atom is empty
space
• electrons orbit the nucleus do not accept references to
shells
AO /
Spec. Ref.
05.3 electrons orbit the nucleus at allow electrons orbit the nucleus 1 AO1
specific distances in energy levels 4.1.1.3
allow electrons orbit the nucleus
in shells
AO /
Spec. Ref.
05.4 ~100 000 times larger 1 AO2
4.1.1.5
AO /
Spec. Ref.
05.5 (surface area = 6 × 1.22 =) AO2
8.64 (nm2) 1 4.2.4.1
(volume = 1.23 =) 1.728 (nm3) 1
(ratio = 8.64 : 1.728 =) allow (ratio = 1.728 : 8.64 =)
8.64 1.728 1
(: 1) (1 :)
1.728 8.64
allow correct use of incorrectly
determined values of surface
area and / or volume
= 5 : 1 allow = 1 : 0.2 1
AO /
Spec. Ref.
05.6 allow converse arguments in AO3
terms of fine particles 4.2.4.2
(nanoparticles) 1
have a higher surface area to
volume ratio
(so) less coating is used (so) a thinner layer can be used 1
OR
(with nanoparticles)
a thinner layer can be used (1) allow less coating is used
(so) more light gets through the allow (so) visibility is not
lenses (1) reduced (as much)
Total Question 5 12
How to answer it
Atomic Structure History & Nanoparticles
This question assesses fundamental knowledge from AQA Specification 4.1.1 (A simple model of the atom) and 4.2.4 (Nanoparticles):
- Recalling historical models of the atom: the plum pudding model and Niels Bohr’s adaptation.
- Understanding how the alpha particle scattering experiment provided evidence for the nuclear model.
- Using powers of ten to estimate orders of magnitude comparing atomic and nuclear sizes.
- Calculating surface area, volume, and the simplest whole-number surface area-to-volume ratio of a cubic particle.
- Explaining the practical advantages of using nanoparticles over fine particles in coatings.
Describing the Plum Pudding Model
AQA Spec 4.1.1.3 • AO1 (Knowledge & Recall)
✅ Correct Answer (Mark Scheme)
Must include both distinct features:
- A ball of positive charge [1 mark]
- With (negative) electrons embedded within it [1 mark]
❌ Common Errors & Misconceptions
- Anachronistic terms: Mentioning protons, neutrons, or a nucleus. These had not yet been discovered!
- Saying electrons "orbit" the charge (that belongs to the later nuclear and Bohr models).
Conclusions from the Alpha Scattering Experiment
AQA Spec 4.1.1.3 • AO1 (Knowledge & Understanding)
✅ Correct Answer (Any Two)
- Most of the atom is empty space [1 mark]
- The mass of the atom is concentrated at the centre / nucleus [1 mark]
- The nucleus has a positive charge [1 mark]
- Electrons orbit the nucleus [1 mark]
🧠 Observation vs. Conclusion
- Observation: Most alpha particles passed straight through. → Conclusion: Atom is mostly empty space.
- Observation: A few were deflected at large angles. → Conclusion: Nucleus is positively charged and contains most mass.
- Mark scheme rule: Do not accept references to "shells" here — electron shells were introduced later by Bohr.
Niels Bohr's Contribution
AQA Spec 4.1.1.3 • AO1 (Knowledge & Recall)
✅ Correct Answer
Electrons orbit the nucleus at specific distances (or in energy levels / shells) [1 mark].
💡 Key Knowledge Timeline
- Dalton: Tiny indivisible spheres.
- Thomson: Plum pudding (electrons found).
- Rutherford: Nuclear model (positive central mass).
- Bohr: Electrons orbit in fixed energy levels (shells).
- Chadwick: Discovered neutrons in the nucleus.
Order of Magnitude: Atom vs Nucleus Radius
AQA Spec 4.1.1.5 • AO2 (Application)
✅ Correct Selection
☑ ~100 000 times larger [1 mark]
📐 Quick Order of Magnitude Check
Radius of nucleus ≈ 1.7 × 10⁻¹⁵ m
Ratio = (1.4 × 10⁻¹⁰) / (1.7 × 10⁻¹⁵) ≈ 10⁻¹⁰ / 10⁻¹⁵ = 10⁵ = 100 000.
Surface Area to Volume Ratio of a Nanoparticle
AQA Spec 4.2.4.1 • AO2 (Mathematical Skills)
📐 Step-by-Step Calculation (Cube side length = 1.2 nm)
A cube has 6 identical square faces.
Area of 1 face = 1.2 × 1.2 = 1.44 nm²
Total surface area = 6 × 1.44 = 8.64 nm² [1 mark]
Volume of a cube = (side length)³ = 1.2 × 1.2 × 1.2 = 1.728 nm³ [1 mark]
Ratio = Surface Area : Volume = 8.64 : 1.728
Divide both sides by 1.728: 8.64 / 1.728 = 5 [1 mark]
Simplest whole-number ratio = 5 : 1 [1 mark]
(Also allowed: 1 : 0.2 if volume : surface area)
❌ Common Calculation Traps
- Forgetting 6 faces: Calculating the area of just 1 face (1.44) instead of multiplying by 6.
- Rounding too early: Rounding 1.728 to 1.7 gives 8.64 : 1.7 ≈ 5.08, causing loss of the final simplest whole ratio mark.
- Unit conversions: Don't convert nm to metres here! Keeping both in nm² and nm³ cancels out units smoothly.
🧠 Quick Check Shortcut for Cubes
For any cube of side length L:
SA / Volume = (6 × L²) / L³ = 6 / L
Here: 6 / 1.2 = 5. Therefore, the ratio is always 5 : 1. Use this formula to instantly verify your answer!
Why Nanoparticles are Used for Coatings
AQA Spec 4.2.4.2 • AO3 (Application & Evaluation)
✅ Correct Explanations (Choose Route 1 or Route 2)
Route 1 (Surface Area focus):
- Nanoparticles have a higher surface area to volume ratio [1 mark]
- Therefore, less coating / a thinner layer is needed (to provide the same protection) [1 mark]
Route 2 (Optical transparency focus):
- A thinner layer / less substance can be applied [1 mark]
- So more light gets through / visibility is not reduced / coating is transparent [1 mark]
🧠 Exam Technique: "Explain why..."
This question awards 1 mark for the feature (higher SA:V ratio or thinner layer) and 1 mark for the consequence (less material needed or clearer glass).
Always link the nano-property directly to why someone buying glasses would want it!
Topics
Chemistry · C1: Atomic Structure and the Periodic Table · C2: Bonding, Structure and the Properties of Matter
Question and mark scheme from the AQA GCSE Chemistry examination, Chemistry Paper 1 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.