GCSE · Chemistry · AQA · Spec 8462

Uses and risks of nanoparticles

Same material, far smaller pieces — and suddenly sunscreen goes invisible and silver starts killing bacteria.

Build the web

Trace every use — and every risk — back to its cause

Nanoparticles have two stand-out features: they're tiny, and they have a very high surface area to volume ratio. Each use and each risk in this web comes from one of them — or both. Draw an arrow from a feature to each thing you think it explains, then compare your web with the lesson's.

  1. Tiny particle size
  2. Invisible sunscreen (titanium dioxide)
  3. Thin, flexible conductive inks (gold and silver)
  4. Possible harm inside our cells
  5. Bacteria-killing silver (dressings, deodorants, socks)
  6. Faster, more efficient catalysts
  7. Very high surface area to volume ratio
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Same stuff, different behaviour

In bulkvsAs nanoparticles

Read across each row: what changes when the same material comes as nanoparticles — and what doesn't?

Focus

Titanium dioxide

In bulk

A white solid used as a pigment. It absorbs harmful UV — and you can see it.

As nanoparticles

Still absorbs harmful UV, but the particles are almost invisible: no white residue.

The insight

The surprise is what stays the same. It's the same substance, doing the same UV job — only now you can't see it.

Silver

In bulk

Not an effective antimicrobial agent.

As nanoparticles

Kills bacteria and inhibits their growth — used in medical dressings, deodorants and sock fabrics.

Gold in electronics

In bulk

A gold-plated headphone jack — not flexible.

As nanoparticles

Gold and silver nanoparticles in conductive inks: electronics that are very thin and very flexible.

Catalysts

In bulk

Low surface area to volume ratio, so less efficient.

As nanoparticles

High surface area to volume ratio: faster, more efficient reactions, and less catalyst needed.

Material families

What is each nanoparticle made from?

Most nanoparticles used in chemistry come from a few families. Pick a nanoparticle, then the family it belongs to.

Still to sort

Metals (0)

A metal element on its own.

Metal oxides (0)

A metal combined with oxygen.

Where the line is: Titanium dioxide contains a metal, but it's a metal oxide — not the metal itself.

Silicates (0)

One of the main families of nanoparticles in chemistry.

Carbon (0)

Some nanoparticles are made from carbon.

5 of 5 still to sort.

What do you think?

So — are nanoparticles safe?

Silver nanoparticles are already in some deodorants and sock fabrics, and titanium dioxide nanoparticles are in sunscreens.

Which is closest to what you think right now?
How sure are you?

Your judgement

Should nanoparticles be in everyday products?

The claim

Nanoparticles should be used in everyday products.

Place each piece of evidence to load the balance. Mark the strong ones — they count double.

  1. Silver nanoparticles in medical dressings kill bacteria and stop them growing.

    Evidence 1: does it support or challenge the claim?

  2. Titanium dioxide nanoparticles give sunscreen UV protection without a white residue.

    Evidence 2: does it support or challenge the claim?

  3. Nanoparticle catalysts make reactions faster and more efficient, so less catalyst is needed.

    Evidence 3: does it support or challenge the claim?

  4. Gold and silver conductive inks could make wearable electronics thin and flexible.

    Evidence 4: does it support or challenge the claim?

  5. Nanoparticles are small enough to pass through cell membranes, into lung cells if inhaled or intestine cells if ingested.

    Evidence 5: does it support or challenge the claim?

  6. Inside cells they could catalyse harmful reactions or carry toxic substances in.

    Evidence 6: does it support or challenge the claim?

  7. Their long-term effects on human health and the environment are not fully understood.

    Evidence 7: does it support or challenge the claim?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

The features that make nanoparticles useful are the same ones behind their possible risks.

What you need to know

  • Nanoparticles have a much higher surface area to volume ratio than the same material in bulk, so their properties are not identical to the bulk material's.
  • Because of that high surface area to volume ratio, smaller quantities of nanoparticles may be needed — for example, less material in a chemical reaction.
  • Most nanoparticles used in chemistry are made from metals, metal oxides or silicates; some are made from carbon.
  • Some uses come from the tiny size (invisible sunscreen, thin flexible conductive inks); others come from the high surface area to volume ratio (bacteria-killing silver, efficient catalysts).
  • Possible risks: nanoparticles are small enough to pass through cell membranes, and inside cells they could catalyse harmful reactions or carry toxic substances in.
  • Nanoparticles are relatively new and not well researched, so their long-term effects on health and the environment aren't fully known — and the risk depends on the type and how it's used.

The big picture

Nanoparticles have a much higher surface area to volume ratio than the same material in bulk, so they don't behave exactly like it. Their tiny size and their huge surface explain what they're used for: invisible sunscreens, thin flexible conductive inks, bacteria-killing silver and efficient catalysts. The same two features explain the possible risks, because nanoparticles are small enough to get into cells. They're also quite new, so their long-term effects aren't fully known, and the benefits have to be weighed against the risks.

Key points

1Nano isn't just 'smaller': a much higher surface area to volume ratio gives nanoparticles different properties from the bulk material.
2Titanium dioxide nanoparticles in sunscreen absorb harmful UV, like the bulk solid, but are almost invisible — no white residue.
3Gold and silver nanoparticles are used as conductive inks, letting electronics be very thin and flexible — useful for wearables.
4Silver nanoparticles kill bacteria and inhibit their growth, so they're used in medical dressings, deodorants and sock fabrics; bulk silver isn't an effective antimicrobial.
5Nanoparticle catalysts have more surface sites for reactions: faster, more efficient, and less catalyst is needed.
6Carbon nanotubes are very strong fibres and excellent conductors of heat and electricity; fullerenes have been suggested as possible drug delivery devices.
7If inhaled, nanoparticles could be absorbed by lung cells; if ingested, they could pass into cells of the intestines.
8Society might respond with more research into long-term effects, improved industry safety and greater public awareness, so people can make informed decisions.

Worked example

Problem

Explain why silver nanoparticles are woven into sock fabrics, when a piece of bulk silver would not do the same job.

⚠ Watch out

Writing that nanoparticles are 'just smaller bits' that behave like the bulk material. Their much higher surface area to volume ratio changes their properties — bulk silver isn't an effective antimicrobial, but silver nanoparticles are.

🧠

Memory hook

Small is the superpower — and the worry. TINY gives you invisible sunscreen, bendy inks and a way into cells. HUGE SURFACE gives you bacteria-killing silver, speedy catalysts and possible harmful reactions inside cells.

✓

Check yourself

A friend says: 'Nanoparticles are so tiny they can't possibly do any harm.' Reply in two sentences, using what you now know about cells.

Flashcards

(14)
How does the surface area to volume ratio of a nanoparticle compare with the same material in bulk?
It's much higher — which is why nanoparticles don't have identical properties to the bulk material.
Why might a smaller quantity of nanoparticles do the job of a larger amount of normal-sized particles?
Their high surface area to volume ratio — for example, less material may be needed in a chemical reaction.
What are most nanoparticles used in chemistry made from?
Metals, metal oxides or silicates. Some are made from carbon.
Titanium dioxide sunscreen: what stays the same as the bulk solid, and what changes?
Same: it absorbs harmful UV radiation. Changes: the particles are almost invisible, so there's no white residue.
Which nanoparticles are used as conductive inks, and what does their small size allow?
Gold and silver. They let electronics be very thin and very flexible — useful for wearable electronics.
Name three products that use silver nanoparticles to kill bacteria.
Medical dressings, deodorants (limiting body odour) and sock fabrics.
Why are nanoparticle catalysts more efficient than bulk catalysts?
More sites on the surface for reactions, so reactions happen faster and more efficiently — and less catalyst is needed.
Describe carbon nanotubes.
Very small, extremely strong fibres (high tensile strength) that are excellent thermal and electrical conductors.
What has it been suggested fullerenes might be used for?
As drug delivery devices — a suggestion, so say 'might be used'.
Where could nanoparticles end up if they are inhaled? If they are ingested?
Inhaled: absorbed by cells in the lungs. Ingested: passed into cells of the intestines. They're small enough to cross cell membranes.
Once inside a cell, what two things could a nanoparticle do?
Catalyse harmful reactions, or carry toxic substances bound to its surface into the cell.
Why are the risks of nanoparticles not fully known?
They're relatively new and not well researched; long-term effects on health and the environment aren't fully understood, and risk varies with type and use.
Give three ways society might respond to the possible risks of nanoparticles.
More research into long-term effects, improved industry safety, and greater public awareness of benefits and risks.
Why is research into nanoparticles such an active area?
They have many applications, and finding new applications for nanoparticulate materials is an important area of research.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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