A company adds cube-shaped silver particles to the plastic lining of food containers to kill bacteria. It tests two linings, J and K. Each lining contains 0.050 g of silver, and both tests use the same type and number of bacteria.
| Lining | Side length of each silver particle in nm | Time taken to kill 99% of the bacteria in minutes |
|---|---|---|
| J | 10 | 30 |
| K | 50 | 150 |
Calculate the surface area to volume ratio of one particle in each lining. Determine how many times greater the ratio is for J than for K.
Give the units of the surface area to volume ratios.
Explain the difference between the times taken for the two linings.
122 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.