The sizes of coarse, fine and nanoparticles, how surface area to volume ratio changes with size, and the uses and possible risks of nanotechnology. Chemistry only content.
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1.What is the size range of nanoparticles?
From 1 to 100 nanometres in diameter, which is a few hundred atoms across.
2.What is the size range of fine particles?
From 100 to 2500 nanometres, sometimes called PM2.5.
3.What is the size range of coarse particles?
From 2500 to 25000 nanometres, sometimes called PM10 or dust.
4.How many metres is one nanometre?
1 x 10 to the power minus 9 metres.
5.How do you calculate the surface area to volume ratio of a cube?
Surface area is 6 times the length squared. Volume is the length cubed. Divide surface area by volume.
6.Calculate the surface area to volume ratio of a cube of side 2 nm.
Surface area = 6 x 4 = 24. Volume = 8. Ratio = 3 to 1.
7.What happens to the surface area to volume ratio as a particle gets smaller?
It increases.
8.If the side of a cube decreases by a factor of 10, what happens to the ratio?
The surface area to volume ratio increases by a factor of 10.
9.Why does a high surface area to volume ratio matter?
Much more of the substance is exposed, so smaller quantities are needed to be effective, and the material can behave very differently from the bulk.
10.Why might a nanoparticle catalyst be better than a bulk one?
Its very large surface area means much less material achieves the same effect, which lowers cost.
11.Give a use of nanoparticles in medicine.
Delivering drugs directly to the cells where they are needed.
12.Give a use of nanoparticles in electronics.
Making very small, very fast electronic circuits and components.
13.Give a use of nanoparticles in cosmetics.
In sun creams, where they give better skin coverage and more effective protection from ultraviolet light than traditional creams.
14.Give a use of nanoparticles in materials.
Deodorants and wound dressings use silver nanoparticles for their antibacterial properties.
15.Why are nanoparticle sun creams considered better in some ways?
They are transparent rather than white, cover the skin more effectively, and use less material.
16.Give a concern about nanoparticles in sun cream.
The long term effects on health are not fully known, and there are questions about whether they can pass through the skin into cells.
17.Why is more research into nanoparticles needed?
Their effects on health and on the environment over a long period have not yet been established, and their behaviour can differ from the same material in bulk.
18.What does bulk material mean?
The same substance in ordinary, much larger pieces rather than as nanoparticles.
19.Why can a nanoparticle have different properties from the bulk material?
Such a large proportion of its atoms are at the surface that surface behaviour dominates.
20.How does a nanoparticle compare in size to an atom?
A nanoparticle is a few hundred atoms across, so it is much larger than an atom but far smaller than anything visible.
21.Why might people be cautious about using nanoparticles widely?
They are a relatively new technology, so there has not been time to study long term risks, and once released into the environment they are hard to recover.
22.Give one advantage and one disadvantage of nanoparticle technology.
Advantage: very effective with small quantities of material because of the huge surface area. Disadvantage: the health and environmental risks are not yet fully understood.
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