Some sunscreens contain nanoparticles of titanium dioxide.
State the size range of nanoparticles.
Give the unit.
A titanium dioxide nanoparticle has a diameter of 30 nm. A typical atom has a diameter of about 0.3 nm.
Calculate about how many atoms would fit in a line across the nanoparticle.
A student models particles as cubes of different sizes.
The table shows the student's results.
| Side length of cube (nm) | Surface area (nm²) | Volume (nm³) | Surface area to volume ratio |
|---|---|---|---|
| 5 | ? | 125 | ? |
| 50 | 15 000 | 125 000 | 0.12 |
| 500 | 1 500 000 | 125 000 000 | 0.012 |
A cube has six faces. The area of one face = side length × side length.
Calculate the surface area of the cube with a side length of 5 nm.
Surface area = ...... nm²
Calculate the surface area to volume ratio of the cube with a side length of 5 nm.
Use the equation: surface area to volume ratio = surface area ÷ volume
Describe the pattern in the surface area to volume ratio shown in the table.
Silver nanoparticles are added to wound dressings to kill bacteria.
Explain why silver nanoparticles kill bacteria better than the same mass of larger silver particles.
Give one possible risk of using nanoparticles in sunscreens.
60 exam-style questions on OCR GCSE Chemistry 2.3 Properties of materials, covering 2.3.1 Carbon bonding and the variety of organic compounds, 2.3.2 Diamond, graphite, fullerenes and graphene, 2.3.3 Bond strength, changes of state and predicting states, 2.3.4 Bulk properties and types of bonding, and 2.3.5 Nanoparticles: scale, surface area, uses and risks. Each one has a worked solution and a mark scheme showing where the marks go.