An artificial hip joint has a stem that fits inside the thigh bone and a ball that moves inside a cup in the hip. Engineers are choosing a material for the ball.
The table shows information about four possible materials.
| Material | Type of material | Density / g cm−3\mathrm{g\,cm^{-3}}gcm−3 | Behaviour under a sudden impact | Corrosion in the body | Rate of wear |
|---|---|---|---|---|---|
| titanium alloy | metal | 4.5 | bends, does not break | none | medium |
| stainless steel | metal | 8.0 | bends, does not break | very slow | medium |
| alumina | ceramic | 3.9 | may crack | none | very low |
| poly(ethene) | polymer | 0.94 | squashes, does not break | none | high |
Metals bend without breaking but ceramics such as alumina may crack. Explain this difference in terms of structure.
The stem of the hip joint is made from stainless steel, an alloy of iron. Explain why an alloy such as stainless steel is harder than pure iron.
Evaluate the four materials for making the ball of the hip joint. Use the information in the table and your knowledge.
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.