Nanoparticles
Master Nanoparticles for GCSE Chemistry with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. A separate (triple) chemistry topic: nanoparticles have a huge surface area to volume ratio, useful in catalysts, sun creams and medicine.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Nanoparticles are particles between 1 and 100 nanometres in size, containing only a few hundred atoms. This is a Triple-only topic.
For comparison, fine particles are between 100 and 2500 nm, and coarse particles between 2500 and 10000 nm. Coarse particles are often referred to as dust.
The key property is surface area to volume ratio. As the side of a cube decreases by a factor of ten, the surface area to volume ratio increases by a factor of ten. This means nanoparticles are far more reactive, so much smaller quantities are needed as catalysts. Uses include sun creams, deodorants, catalysts and medicine, though the long-term health effects are not fully known.
Revision notes
Sizes
Nanoparticles: 1 to 100 nm, containing only a few hundred atoms.
Fine particles: 100 to 2500 nm. Coarse particles: 2500 to 10000 nm, often called dust. Nanoparticles are between 100 and 1000 times smaller than atoms are large.
Surface area to volume ratio
As the side of a cube decreases by a factor of ten, the surface area to volume ratio increases by a factor of ten.
This is why nanoparticles have such high reactivity — a far greater proportion of their atoms are on the surface where reactions occur.
Uses and risks
Uses: catalysts requiring much smaller quantities, sun creams giving better skin coverage and protection, deodorants, and medicine.
Risks: the effects on health are not fully understood, particularly whether nanoparticles can enter the body and accumulate in organs.
Key points
- Nanoparticles are 1 to 100 nm in size.
- Fine particles are 100 to 2500 nm.
- Coarse particles are 2500 to 10000 nm.
- Reducing the side by ten increases the ratio by ten.
- High surface area to volume makes them very reactive.
- Long-term health effects are not fully known.
Worked examples
Example 1
State the size range of nanoparticles. [1 mark]
Model answer
Between 1 and 100 nanometres (1 mark).
Example 2
Explain why nanoparticles are useful as catalysts. [3 marks]
Model answer
Nanoparticles have a very high surface area to volume ratio (1 mark), so a much greater proportion of their atoms are on the surface where reactions take place (1 mark). This makes them highly reactive, so much smaller quantities are needed than with conventional catalysts (1 mark).
Example 3
Give one advantage and one risk of using nanoparticles in sun creams. [2 marks]
Model answer
Advantage: they give better skin coverage and more effective protection from ultraviolet light (1 mark). Risk: the long-term effects on health are not fully known, and they may be able to enter the body and accumulate (1 mark).
Common mistakes
Confusing the size ranges.
Nanoparticles 1–100 nm, fine 100–2500 nm, coarse 2500–10000 nm.
Saying nanoparticles are reactive because they are small.
The reason is the high surface area to volume ratio.
Giving only advantages.
Evaluation questions require the health risks as well.
Forgetting this is Triple-only.
It is not required for Combined Science.
Exam tips
- Learn all three size ranges precisely.
- Explain reactivity through surface area to volume ratio.
- Give both a use and a risk when evaluating.
- Remember this is a Triple-only topic.
Key terms
- Nanoparticle
- A particle between 1 and 100 nanometres in size.
- Surface area to volume ratio
- The comparison determining reactivity.
- Fine particle
- A particle between 100 and 2500 nanometres.
- Nanometre
- One billionth of a metre.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.