Properties and uses of some metals
4 marks · NormalThe diagrams show a pure metal and an alloy. Use your knowledge of structure and properties to answer the questions.
Describe the arrangement of atoms in a pure metal.
Explain why the alloy is harder than the pure metal.
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(a) Atoms are arranged in regular layers (lattice), all the same size.
(b) The alloy contains atoms of different sizes which disrupt the regular arrangement. This makes it difficult for the layers to slide, so the alloy is harder. · must show different sizes, disrupted layers, harder because layers slide less
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Marking points
B1 (a) · 1 mark · Describes pure metal atoms as being in regular layers or a regular lattice and all the same size.
M1 (b) · 1 mark · States that different sized atoms disrupt the arrangement/lattice.
M2 (b) · 1 mark · Mentions that this makes it difficult for layers to slide over each other.
A1 (b) · 1 mark · Explains that this structural change results in increased hardness.
Worked solution
a) In a pure metal, atoms are arranged in regular, repeating layers and are all the same size.
b) In an alloy, atoms of different sizes disrupt the regular arrangement. This stops the layers from sliding easily and makes the alloy much harder than the pure metal.