Question bank › GCSE Chemistry › Bonding, structure, and the properties of matter
Nanoparticles (Chem only)
Answer on paper first, then reveal the mark scheme one mark at a time.
1Grade 6–7Triple only5 marks
Nanoparticles of a catalyst are cube-shaped with sides of 20 nm.
(a) Calculate the surface area to volume ratio of one nanoparticle. [3]
(b) The side length of a cube is decreased by a factor of 10. State what happens to the surface area to volume ratio. [1]
(c) Give one reason why less of a catalyst is needed when it is in the form of nanoparticles. [1]
(a) surface area $= 6 \times 20^2 = 2400\ \text{nm}^2$(1)
(a) volume $= 20^3 = 8000\ \text{nm}^3$(1)
(a) ratio $= 0.3\ (\text{nm}^{-1})$ allow 3 : 10 or 0.3 : 1(1)
(b) increases by a factor of 10(1)
(c) larger surface area to volume ratio (so a smaller mass has the same surface area for reactions)(1)
Answer: (a) 0.3 nm⁻¹ (2400 : 8000) (b) increases ×10 (c) much larger surface area to volume ratio
Examiner tip: Area is length², volume is length³ — getting these mixed up costs two marks at once.
2Grade 1–3FoundationTriple only3 marks
This question is about nanoparticles.
(a) What is the size range of nanoparticles?
Tick (✓) one box.
☐ 0.01 nm to 1 nm
☐ 1 nm to 100 nm
☐ 100 nm to 2500 nm
☐ 2500 nm to 10 000 nm
[1]
(b) About how many atoms does a nanoparticle contain?
Tick (✓) one box.
☐ fewer than ten
☐ a few hundred
☐ about one million
☐ about 6 × 1023
[1]
(c) Which of these is equal to 1 nm?
Tick (✓) one box.
☐ 1 × 10−3 m
☐ 1 × 10−6 m
☐ 1 × 10−9 m
☐ 1 × 10−12 m
[1]
(a) 1 nm to 100 nm if more than one box ticked, no mark(1)
(b) a few hundred if more than one box ticked, no mark(1)
(c) 1 × 10−9 m if more than one box ticked, no mark(1)
Answer: (a) 1 nm to 100 nm (b) a few hundred (c) 1 × 10−9 m
Examiner tip: 100 nm to 2500 nm is the range for fine particles (PM2.5), not nanoparticles — learn the three size ranges as a set.
3Grade 4–5Triple only4 marks
Gold nanoparticles are used in some medical tests.
One gold nanoparticle has a diameter of 15 nm. The diameter of a gold atom is 0.3 nm.
(a) How many times bigger is the diameter of the gold nanoparticle than the diameter of a gold atom? [1]
(b) Give the diameter of the gold nanoparticle in metres.
Give your answer in standard form. [2]
(c) Some particles in smoke have a diameter of 1.2 × 10−6 m.
How many times bigger is the diameter of a smoke particle than the diameter of the gold nanoparticle? [1]
(a) 50 (times)(1)
(b) 15 × 10−9 (m) allow 0.000 000 015 (m)(1)
(b) 1.5 × 10−8 (m) correct answer with no working scores 2 marks; 1.5 × 10−9 or 15 × 10−8 scores 0 for this mark(1)
(c) 80 (times) allow ecf from (b): 1.2 × 10−6 ÷ their (b) correctly evaluated(1)
Answer: (a) 50 (b) 1.5 × 10−8 m (c) 80
Examiner tip: Write 15 nm as 15 × 10−9 m first, then move the decimal point — many students write 1.5 × 10−9 and lose the second mark.
4Grade 4–5Triple only4 marks
The table shows the diameters of four particles, P, Q, R and S.
Particle
Diameter
P
6.0 × 10−6 m
Q
45 nm
R
8.0 × 10−7 m
S
3.0 × 10−10 m
1 nm = 1 × 10−9 m
(a) Which particle is a nanoparticle? [1]
(b) Which particle is a coarse particle (PM10)? [1]
(c) Which particle is a fine particle (PM2.5)? [1]
(d) A student says that particle S is a nanoparticle because it is very small.
Explain why the student is wrong. [1]
(a) Q(1)
(b) P(1)
(c) R(1)
(d) S is 0.3 nm (diameter), which is smaller than 1 nm / below the nanoparticle range (1–100 nm) allow it is the size of an atom / small molecule; ignore it is too small without reference to 1 nm or the size of atoms(1)
Answer: (a) Q (b) P (c) R (d) S is 0.3 nm, below the 1–100 nm range — it is atom-sized
Examiner tip: Convert every diameter into nm before comparing: 8.0 × 10−7 m is 800 nm, which is a fine particle, not a nanoparticle.
5Grade 6–7Triple only5 marks
The diagram shows a cube-shaped nanoparticle of zinc oxide.
(a) Calculate the surface area to volume ratio of the nanoparticle.
Give your answer as a simple ratio. [3]
(b) A powder of zinc oxide contains cube-shaped particles with sides of 3 µm.
1 µm = 1000 nm
How many times larger is the surface area to volume ratio of the nanoparticle than the surface area to volume ratio of a powder particle? [2]
(a) surface area = 6 × 3 × 3 = 54 (nm2)(1)
(a) volume = 3 × 3 × 3 = 27 (nm3)(1)
(a) 2 : 1 allow 54 : 27 for 2 marks only; allow 2 (nm−1) for 3 marks(1)
(b) powder particle: SA : V = 54 000 000 : 27 000 000 000 / 0.002 : 1 allow side = 3000 nm; allow 1 : 500(1)
(b) 1000 (times) allow ecf from (a); allow 1000 from side length decreasing by a factor of 1000(1)
Answer: (a) 2 : 1 (b) 1000 times
Examiner tip: Surface area of a cube is 6 faces × side²; forgetting the 6 (giving 9 : 27) is the most common slip.
6Grade 8–9HigherTriple only5 marks
A cube of zinc oxide has sides of 1.0 µm.
The cube is broken up into nanoparticles. Each nanoparticle is a cube with sides of 50 nm.
1 µm = 1000 nm
(a) Calculate the number of nanoparticles formed. [2]
(b) Calculate how many times larger the total surface area of all the nanoparticles is than the surface area of the original cube. [3]
(a) 203 = 8000 correct answer with no working scores 2 marks(1)
(b) surface area of original cube = 6 × 10002 = 6 × 106 (nm2) allow 6 (µm2)(1)
(b) total surface area of nanoparticles = 8000 × 6 × 502 = 1.2 × 108 (nm2) allow ecf from (a); allow 120 (µm2)(1)
(b) 20 (times) allow ecf; correct answer scores 3 marks; allow 20 from the side length decreasing by a factor of 20 (1000 ÷ 50) with the total volume unchanged(1)
Answer: (a) 8000 (b) 20 times
Examiner tip: Breaking a cube into smaller cubes keeps the total volume the same, so the total surface area goes up by the same factor that the side length goes down.
7Grade 6–7Triple only5 marks
Gold nanoparticles can be used as a catalyst.
A scientist used the same mass of gold each time but with particles of different diameters. She measured the relative rate of the reaction.
The graph shows her results.
(a) Describe the trend shown by the graph. [1]
(b) Use the graph to find the relative rate of reaction when the diameter of the gold particles is 5 nm. [1]
(c) Use the graph to describe what happens to the relative rate of reaction when the diameter of the particles is doubled from 3 nm to 6 nm. [1]
(d) Explain why smaller gold particles give a faster rate of reaction. [2]
(a) as the diameter (of the particles) increases, the rate of reaction decreases allow converse; allow smaller particles give a faster rate; ignore inversely proportional unless trend direction stated(1)
(b) 3.6 allow 3.5 to 3.7(1)
(c) the rate halves / decreases from 6 to 3 allow decreases by a factor of 2; allow ‘decreases’ with correct values quoted for both 3 nm and 6 nm(1)
(d) (smaller particles have a) larger surface area to volume ratio allow larger (total) surface area (for the same mass); do not accept ‘larger surface area’ for a single particle(1)
(d) so more (gold) atoms are on the surface / more surface for the reacting particles to collide with / react on allow more frequent (successful) collisions; ignore ‘more collisions’ without reference to rate or frequency(1)
Answer: (a) rate decreases as diameter increases (b) 3.6 (c) it halves (6 → 3) (d) larger SA : V, so more surface for reactant particles to collide/react on
Examiner tip: In (d) say ‘surface area to volume ratio’ (or total surface area for the same mass) — a single smaller particle actually has a smaller surface area.
8Grade 1–3FoundationTriple only4 marks
Some sun creams contain nanoparticles of titanium dioxide. The nanoparticles absorb ultraviolet (UV) light.
Older sun creams contained much larger particles of titanium dioxide. These sun creams left a white layer on the skin.
(a) Give one advantage of using nanoparticles of titanium dioxide in sun cream. [1]
(b) Give two possible risks of using nanoparticles in sun cream. [2]
(c) Give one other use of nanoparticles. [1]
(a) any one from: (sun cream is) transparent / does not leave a white layer; gives better skin coverage; gives better protection from UV / sunburn / skin cancer; less titanium dioxide needed ignore ‘it is cheaper’ unless linked to less needed(1)
(b) any two from: nanoparticles may be absorbed through the skin / get into the body / into (body) cells; may be breathed in (if sprayed); long-term effects (on health) are not yet known / not fully tested; may harm the environment / aquatic life when washed off (into water)(1)
(b) second risk from the list above ignore ‘they are toxic’ or ‘they are dangerous’ unqualified(1)
(c) any one from: in medicine / drug delivery; in electronics; in cosmetics (other than sun cream); in deodorants; as catalysts allow named example of each, e.g. silver nanoparticles in wound dressings; do not accept sun cream(1)
Answer: (a) transparent / better coverage and UV protection (b) e.g. absorbed into the body or cells; long-term effects unknown; harm to the environment when washed off (c) e.g. catalysts, drug delivery, electronics, deodorants
Examiner tip: ‘They might be harmful’ scores nothing — say how: absorbed through skin, breathed in, effects not yet known or released into water.
9Grade 6–7Triple only6 marks
Silver kills bacteria. A company wants to use silver nanoparticles in two products:
sports socks, to stop them smelling
dressings for burns and wounds, to reduce infection.
The table shows some information.
Form of silver
Particle size
Mass of silver needed per dressing to kill 99% of bacteria in mg
silver powder
10 µm
120
silver nanoparticles
20 nm
6
Other information:
Tests showed that 35% of the silver nanoparticles were washed out of the socks after ten washes.
Silver nanoparticles are small enough to pass into cells.
Some bacteria in sewage treatment works are useful.
There is little long-term data on the effects of silver nanoparticles on people or the environment.
Evaluate the use of silver nanoparticles in the two products.
Use the information and your own knowledge. [6]
Benefits: nanoparticles need a much smaller mass of silver (6 mg vs 120 mg; 20 times less)(1)
because nanoparticles have a (much) larger surface area to volume ratio (so more silver atoms are exposed to bacteria)(1)
less silver used, so cheaper / conserves a limited resource(1)
dressings: reduce infection of burns / wounds — a real medical benefit; socks: stop smell / odour(1)
Risks: silver washed out of socks enters wastewater / rivers — 35% lost after ten washes(1)
could kill useful bacteria in sewage treatment / harm aquatic organisms(1)
nanoparticles can pass into (skin / body) cells — more likely through a wound or burn / broken skin(1)
long-term effects (on health or the environment) are not yet known / little long-term data(1)
socks lose their antibacterial effect over time as silver is washed out(1)
Judgement: e.g. use in dressings is justified because the medical benefit outweighs the risk / used for a short time and disposed of (not washed); use in socks is harder to justify because the benefit is cosmetic and silver repeatedly enters the environment(1)
A judgement in either direction is credited if supported by the information(1)
Level
Marks
What it looks like
Level 3
5–6
A balanced evaluation that weighs benefits against risks for both products, uses the data (e.g. the 20-fold smaller mass or the 35% washout) and links the smaller mass to surface area to volume ratio. Reaches a reasoned judgement that is supported by the points made.
Level 2
3–4
Gives both benefits and risks, with some use of the information. Some points are linked or explained, but the answer may focus on one product or the judgement may be missing or not fully supported.
Level 1
1–2
Simple statements of a benefit or a risk, mostly copied from the information without explanation. No judgement, or a judgement with no support.
No relevant content
0
No relevant content.
Answer: Nanoparticles need 20× less silver (larger SA : V) and dressings reduce infection, but silver washes out of socks (35% after 10 washes), may kill useful sewage bacteria and can enter cells, with unknown long-term effects. Justified judgement, e.g. dressings yes, socks no.
Examiner tip: ‘Evaluate’ needs a conclusion — top-level answers weigh benefits against risks for each product and finish with a reasoned judgement.
10Grade 8–9HigherTriple only5 marks
A model of a cube-shaped nanoparticle has 6 atoms along each edge.
The diagram shows one layer of atoms from the middle of the cube.
(a) Calculate the total number of atoms in the nanoparticle. [1]
(b) The atoms that are not at the surface form a smaller cube inside the nanoparticle.
Calculate the percentage of atoms in the nanoparticle that are at the surface. [2]
(c) In a larger particle of the same substance with 60 atoms along each edge, 9.7% of the atoms are at the surface.
Explain how this information helps to explain why nanoparticles have different properties from larger particles of the same substance. [2]
(a) 63 = 216(1)
(b) atoms inside = 43 = 64 and atoms at surface = 216 − 64 = 152 allow ecf from (a)(1)
(b) 152 ÷ 216 × 100 = 70(.4)% allow 70.37%; correct answer with no working scores 2 marks(1)
(c) a much larger proportion / fraction of atoms is at the surface in the nanoparticle (about 70% compared with about 10%) allow nanoparticle has a much larger surface area to volume ratio(1)
(c) (only) surface atoms can react / be in contact with other substances, so the nanoparticle is more reactive / a better catalyst / behaves differently ignore ‘they are smaller’ alone(1)
Answer: (a) 216 (b) 70.4% (c) ~70% vs ~10% of atoms at the surface: much larger SA : V, and surface atoms are the ones that react or interact, so properties differ
Examiner tip: The atoms inside form a cube 2 atoms shorter on each edge (one layer is removed from each side), so it is 4 × 4 × 4, not 5 × 5 × 5.
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