A company wants to choose a form of zinc oxide for a sun cream. The sun cream must be transparent on the skin. The table gives information about three forms of zinc oxide.
Table: The particle diameter and the appearance on the skin of three forms of zinc oxide, J, K and L
| Form of zinc oxide | Particle diameter in nm | Appearance on the skin |
|---|---|---|
| J | 40 | transparent |
| K | 400 | slightly white |
| L | 4000 | white |
Which form of zinc oxide should the company choose, and why?
J, because its particles are nanoparticles and it is transparent
K, because its particles are fine particles and it is only slightly white
L, because its particles are coarse particles and they stay on the skin
J, because its particles are fine particles and they block more of the light
40 exam-style questions on AQA GCSE Chemistry 2.4 Bulk and surface properties of matter including nanoparticles, covering 2.4.1 Sizes of particles and their properties and 2.4.2 Uses of nanoparticles. Each one has a worked solution and a mark scheme showing where the marks go.