A builder compares two materials that can cover the same area of roof.
The table shows part of a life-cycle assessment for enough material to cover 1 m21\,\mathrm{m^{2}}1m2 of roof.
| Life-cycle measure | Clay tiles | Steel sheets |
|---|---|---|
| Percentage recycled at disposal (%) | 12 | 88 |
| Carbon dioxide released when obtaining raw materials (kg) | 4.2 | 8.7 |
| Energy used during manufacture (MJ) | 120 | 85 |
Which conclusion about the overall environmental impact is supported by the data?
Each material is better on at least one measure, so the data do not show which has the lower overall impact.
Clay tiles have the lower overall impact, because obtaining their raw materials releases less carbon dioxide.
The two materials have the same overall impact, because the advantages of each material cancel each other out.
Steel sheets have the lower overall impact, because they are better than clay tiles on two of the three measures.
136 exam-style questions on OCR GCSE Chemistry 6.1 Improving processes and products, covering 6.1.1 Extracting metals industrially and by electrolysis, 6.1.2 Life cycle assessment and recycling, 6.1.3 Biological methods of metal extraction, 6.1.4 The Haber process and the production of fertilisers, 6.1.5 Alloys and their uses, 6.1.6 Corrosion and its prevention, 6.1.7 Comparing and selecting materials, and 6.1.8 Industrial conditions, rate and position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.