The Nano World
How small a nanoparticle is, how the surface-area-to-volume ratio grows as particles shrink, why that makes nanoparticles useful in medicine, electronics, sun cream and catalysts, and why their risks are not yet fully known.
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How small is small?
A nanoparticle is so small that millions could sit on a full stop. At that scale materials start to behave in new and useful ways. This module looks at how particles are sized, how their surface-area-to-volume ratio changes as they shrink, why that makes them so useful, and why scientists are still careful about the risks.
Nano words to know
Learn these before you sort the sizes and uses.
Small against large
Shrinking a particle changes its surface-area-to-volume ratio.
Reason from the size
In the exam, start with the size. The smaller a particle, the greater its surface-area-to-volume ratio, and that is the key to almost every use. Link the large ratio to the job, such as a faster catalyst that needs less material. Report the risks fairly, as effects that are not yet fully understood.
Match the size
- nanoparticle
- fine particle
- coarse particle
- a grain of sand
- 1 to 100 nm across
- 100 to 2500 nm across
- 2500 to 10000 nm across
- far larger than all of these
Match the use
- sun cream
- drug delivery
- catalysts
- electronics
- blocks rays while looking clear on skin
- carries medicine to the right place
- speeds reactions using less material
- makes very small components
What happens to the ratio?
What happens to the surface-area-to-volume ratio as particles get smaller?
- It increases.
- It decreases.
- It stays the same.
- It becomes zero.
Uses of nanoparticles
Select the TWO real uses of nanoparticles.
- In sun cream to protect skin
- As efficient catalysts
- As building bricks for houses
- As the main fuel in a car engine
Work out the ratio
A cube of side 2 has a surface area of 24 and a volume of 8. Divide the surface area by the volume to find the surface-area-to-volume ratio. What is the answer?
Order by size
Put these in order from smallest to largest.
- a nanoparticle
- a fine particle
- a coarse particle
- a grain of sand
Complete the facts
Nanoparticles are tiny, from 1 to 100 _____ across. As particles get smaller, their surface-area-to-volume ratio _____. This makes them useful as _____, because a reaction can happen using less material. Because they are so new, the possible _____ to health are not yet fully known.
Spot the nano uses
Tap the TWO things that really use nanoparticles.
- sun cream
- targeted drug delivery
- ordinary window glass
- a house brick
Choose the reason
Read each case and choose the best answer.
- A catalyst works faster when it is made of nanoparticles. What mainly explains this?
- A sun cream uses nanoparticles instead of a thick white paste. What is the benefit?
- A scientist is asked if nanoparticles are completely safe. What is the fairest answer?
Explain the nano world
Explain why nanoparticles are useful, using the surface-area-to-volume ratio, and say why scientists are still careful about them.
- Say how big a nanoparticle is and what happens to the ratio as size falls
- Give one use and link it to the high ratio
- Explain why the risks mean scientists are careful