Students should consider advantages and disadvantages of the applications…

The idea

Nanoparticles are particles between about 1 nm and 100 nm across, so they have a very large surface area to volume ratio. This gives nanoparticulate materials useful properties: they can be effective catalysts, they can carry tiny amounts of a substance into the body, and they can give smooth, lightweight coatings. For example, a sunscreen containing titanium dioxide nanoparticles spreads easily and gives good protection, but the particles may enter cells and their long-term effect is uncertain. You are not required to recall extra examples or properties beyond those taught; instead, use the information given in a question to judge whether a use is worthwhile.

What earns the marks

• State that nanoparticles have a very large surface area to volume ratio, which makes them effective catalysts and allows small quantities to have a large effect.
• Describe a benefit of a named application, such as improved coverage, lower mass or more efficient delivery of a substance.
• Describe a disadvantage, such as possible toxicity, unknown long-term health effects or environmental harm.
• Use information supplied in the question to reach a justified judgement about whether a particular use is suitable for the stated purpose.
• Recognise that the same property, such as small size, can be both an advantage and a disadvantage depending on the application.

Common mistakes and how to put them right

• Treating all nanoparticles as automatically harmful.

  Put it right: The correct approach is to weigh evidence for the specific use rather than assume a general danger.

• Confusing nanoparticles with atoms or molecules.

  Put it right: Nanoparticles are much larger than individual atoms and contain many atoms, so descriptions should refer to particles in the 1 nm to 100 nm range.

• Giving only advantages or only disadvantages when the question asks for a balanced consideration.

  Put it right: Include at least one point on each side before judging.

Exam tips

• Read the purpose stated in the question and link each advantage or disadvantage directly to that purpose rather than listing general facts.
• Use comparative language such as more effective, less mass or greater risk to make the weighing of evidence clear.
• Finish with a short judgement that follows from the points you made, for example that the benefit outweighs the risk for this use.