Why is an alloy usually harder than the pure metal it is made from?
The atoms in an alloy are held together by covalent bonds not metallic bonds
The atoms in an alloy are all the same size so the layers pack very closely
The different sized atoms distort the layers so they cannot slide over each other
The delocalised electrons in an alloy are held much more tightly by the nuclei
40 exam-style questions on AQA GCSE Chemistry 10.3 Using materials, covering 10.3.1 Corrosion and its prevention, 10.3.2 Alloys as useful materials, and 10.3.3 Ceramics, polymers and composites. Each one has a worked solution and a mark scheme showing where the marks go.