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Unlock This CourseRemember, nanoparticles have a very high surface area to volume ratio. This gives them two big advantages:
Because of this, nanoparticles have many applications. The spec lists five areas: medicine, electronics, cosmetics and sun creams, deodorants and catalysts. Scientists are still finding new uses, so new applications for nanoparticulate materials are an important area of research.
Key terms:
Nanoparticles in sun cream block UV light but rub in clear, so no ghostly white streaks
You do not need to learn specific named examples for the exam. If a question needs one, it will give you the information. But knowing a few common examples makes the ideas easier to follow.
Nanoparticles are so small they can travel around the body and get into cells. Scientists are researching ways to use them to carry medicines to exactly where they are needed, such as a tumour. This could mean a smaller dose and fewer side effects.
Some nanoparticles conduct electricity. Their tiny size helps make very small electronic parts and circuits, so devices can be smaller and lighter.
Nanoparticles of titanium dioxide and zinc oxide are used in sun creams. They block harmful ultraviolet (UV) light from the Sun, which protects the skin. Because the particles are so small, the cream rubs in clear instead of leaving white marks. Nanoparticles are also used in some cosmetics, such as moisturisers.
Silver nanoparticles kill bacteria. Bacteria on the skin cause body odour, so silver nanoparticles can be added to deodorants. For the same reason they are added to some fabrics, such as socks.
Catalysts work at their surface. Nanoparticles have a huge surface area for their volume, so they make very good catalysts. Less material is needed, which matters when the catalyst is an expensive metal.
In almost every use, the benefit comes from the same two ideas: the tiny size, and the high surface area to volume ratio. Use these ideas when you explain any use, even one you have never seen before.
You will learn exactly how catalysts speed up reactions later in the course, in the lesson called Catalysts.
Scientists handle nanoparticles carefully because they are small enough to get into the body, and their long-term effects are not yet fully known
The same features that make nanoparticles useful could also make them harmful. You need to be able to explain that there are possible risks. The key word is "possible": scientists do not yet know for sure.
This is why more research is needed. Some people argue that products containing nanoparticles should be tested more carefully and clearly labelled, so people can choose whether to use them.
Question: A company wants to add silver nanoparticles to sports socks to stop them smelling. Evaluate this use.
Step 1, advantages: silver nanoparticles kill bacteria, so they stop the bacteria that cause the smell. Only a small amount is needed because of the high surface area to volume ratio.
Step 2, disadvantages: the nanoparticles may come out in the wash and enter rivers, where they could harm useful bacteria. They might pass through the skin. The long-term effects are not known.
Step 3, judgement: for example, "The socks would work well, but because the risks to health and the environment are not yet known, more research should be done before they are widely sold."
You could also judge the other way, for example "only a tiny amount of silver is used, so the benefit is worth it". Either judgement can get the marks, as long as it is backed by reasons from both sides.
In the exam you will usually be given some information, such as a table or a short passage, about a product. Use it. Examiners want to see that you have read the data, not just written learned facts.
Give the advantages, linked to small size or high surface area to volume ratio.
Give the possible risks: getting into the body, unknown effects, harm to the environment.
Say whether you think it should be used, and give a reason. Mention the need for more research if the risks are unknown.
Saying nanoparticles are definitely dangerous. The spec says "possible risks". Write "may" or "could", because the effects are not yet fully known.
Only giving one side. An evaluation needs both advantages and disadvantages, plus a conclusion. One-sided answers lose marks.
Not explaining why. "Nanoparticles are good catalysts" is not enough. Add "because they have a high surface area to volume ratio".
Ignoring the information given. If the question gives you data, quote it in your answer.
A sun cream contains nanoparticles of zinc oxide. Older sun creams contained larger particles of zinc oxide.
| Sun cream | Size of zinc oxide particles | Looks on skin | Blocks UV light? |
|---|---|---|---|
| A (older) | larger than 100 nm | white | yes |
| B (newer) | about 30 nm | clear | yes |
(a) Give one advantage of using sun cream B. Use the table. [1 mark]
(b) Explain why some people are worried about using sun cream B. [2 marks]
(c) Suggest why scientists say more research is needed into sun creams like B. [1 mark]
(a) It goes on clear, so it does not leave white marks, but it still blocks UV light (1).
(b) The nanoparticles are so small they may pass through the skin and into the body (1). Nanoparticles can have different properties from the bulk material, so their effects on cells are not fully known and they could be harmful (1).
(c) The long-term effects of nanoparticles on health and the environment are not yet known (1).
For any nanoparticle question, link your answer to size or surface area to volume ratio. For risks, always use careful words like "may" and "could", and mention that more research is needed.