10.8 Alloys
5 exam questions worth 9 marks. Write your answer, open the mark scheme, then give yourself the marks you earned. Your answers are saved on this device.
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Which metals are mixed to make brass?
Choose one answer.
Correct Not quite: the answer is Copper and zinc
Mark scheme
B
Model answer
B: brass is an alloy of copper and zinc.
Calculate the percentage of gold in 18 carat gold.
Mark scheme
- 18 ÷ 24 × 100 = 75% (1)
Model answer
18 ÷ 24 × 100 = 75%
Explain why alloys are harder than pure metals.
Mark scheme
- pure metals have regular layers that slide over each other (1)
- in an alloy, atoms of different sizes distort the layers (1)
- so the layers cannot slide as easily (1)
Model answer
In a pure metal, the atoms are in regular layers that can slide over each other easily. In an alloy, atoms of a different size distort the layers, making it harder for them to slide, so the alloy is harder.
Explain why stainless steel is used to make cutlery.
Mark scheme
- it resists corrosion / does not rust (1)
- it is hard / strong (1)
Model answer
Stainless steel resists corrosion and is hard, so it lasts a long time when washed.
Suggest why aluminium alloys are used to build aircraft.
Mark scheme
- low density / light (1)
- strong (1)
Model answer
Aluminium alloys are light (low density) but strong.
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