Sizes of particles and their properties (chemistry only)
Practise 26 exam-style questions on Sizes of particles and their properties (chemistry only) for AQA GCSE Chemistry. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
26 questions
1–6 marks each
Instant marking
No sign-up needed
20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
How many metres is 1 nanometre (1 nm)? Write 100 nm in metres, in standard form.
Model answer
1 nm = 1 × 10⁻⁹ m 100 nm = 100 × 10⁻⁹ m = 1 × 10⁻⁷ m
Explanation
'Nano' means one thousand-millionth. Multiplying 10⁻⁹ by 100 (10²) gives 10⁻⁷, so the largest nanoparticles are 1 × 10⁻⁷ m across.
Mark scheme
1 mark
1 nm = 1 × 10⁻⁹ m
allow 0.000 000 001 m
1 mark
100 nm = 1 × 10⁻⁷ m
must be in standard form; allow ecf from an incorrect value for 1 nm
Question 2
2 marks
Put these in order of size, starting with the smallest: a coarse dust particle (PM10) an atom a fine particle (PM2.5) a nanoparticle
Model answer
Atom (about 0.1 nm radius), nanoparticle (1-100 nm), fine particle (100-2500 nm), coarse dust particle (2500-10 000 nm).
Explanation
Each category in this list is larger than the one before. Nanoparticles are made of hundreds of atoms, and they are smaller than fine particles (PM2.5), which in turn are smaller than coarse particles (PM10).
Mark scheme
1 mark
atom, nanoparticle, fine particle, coarse particle
2 marks for all four in the correct order
1 mark
1 mark if only one pair of neighbouring items is swapped
Question 3
3 marks
A student says: 'Nanoparticles are so small that they are about the same size as atoms.'
Explain why the student is wrong.
Model answer
Atoms have a radius of only about 0.1 nm, but nanoparticles are 1-100 nm across. So even the smallest nanoparticles are several times wider than an atom, and the largest are hundreds of times wider; a nanoparticle typically contains a few hundred atoms.
Explanation
Comparing nanoscale dimensions with atoms and molecules is a specification skill. Nanoparticles are tiny compared with everyday objects, but they are still much larger than individual atoms and small molecules.
Mark scheme
1 mark
atoms have a radius of about 0.1 nm / 1 × 10⁻¹⁰ m
allow diameter of about 0.2 nm
1 mark
nanoparticles are 1-100 nm across
1 mark
so nanoparticles are many times larger than atoms / contain a few hundred atoms
allow a correct numerical comparison
Question 4
4 marks
A nanoparticle is a cube with sides of 50 nm. A coarse dust particle is a cube with sides of 5000 nm.
Calculate the surface area to volume ratio of each particle, in nm⁻¹ (per nm). How many times greater is the ratio for the nanoparticle?
Model answer
Nanoparticle: surface area = 6 × 50 × 50 = 15 000 nm²; volume = 50 × 50 × 50 = 125 000 nm³ ratio = 15 000 ÷ 125 000 = 0.12 per nm Coarse particle: surface area = 6 × 5000 × 5000 = 1.5 × 10⁸ nm²; volume = 5000³ = 1.25 × 10¹¹ nm³ ratio = 1.5 × 10⁸ ÷ 1.25 × 10¹¹ = 0.0012 per nm 0.12 ÷ 0.0012 = 100, so the nanoparticle's ratio is 100 times greater.
Explanation
The side length decreases by a factor of 100 (5000 to 50), so the surface area to volume ratio increases by a factor of 100, matching the rule for a factor of 10. For a cube the ratio is always 6 ÷ side length, which is a useful check.
Mark scheme
1 mark
nanoparticle: surface area = 6 × 50² = 15 000 nm² and volume = 50³ = 125 000 nm³
allow use of ratio = 6 ÷ side length; correct answer with no working scores full marks
