A student makes fibreglass rods containing different percentages of glass fibre and measures the force needed to break each rod three times.
| Glass fibre (%) | 0 | 20 | 40 | 60 | 80 |
|---|---|---|---|---|---|
| Mean breaking force (N) | 20 | 45 | 70 | 90 | 60 |
| Range of repeats (N) | 19 to 21 | 44 to 46 | 68 to 71 | 89 to 92 | 59 to 61 |
The student concludes: "The more glass fibre a rod contains, the stronger it is."
Which evaluation of this conclusion is correct?
Not supported: strength rises up to 60% fibre but falls at 80%, so there is an optimum fibre content
Supported: every increase in the percentage of glass fibre gave an increase in the breaking force
Not supported: the rod with 0% fibre shows that the polymer alone is stronger than the composite
Supported: the 80% result is an anomaly and should be ignored, because the other results fit
36 exam-style questions on Edexcel GCSE Chemistry 10.5 Bulk and surface properties of matter including nanoparticles, covering 10.5.1 Nanoparticles: size, uses and risks and 10.5.2 Comparing and selecting materials. Each one has a worked solution and a mark scheme showing where the marks go.