1. 1
   A cutlery manufacturer is choosing a material for a new range of knives and forks. They reject pure iron because it rusts easily and instead choose stainless steel, a mixture of iron with chromium, nickel and carbon.

   (a)

   What term describes a mixture of a metal with one or more other elements, such as stainless steel?

   [1 mark]

   • AA polymer
   • BAn isotope
   • CAn alloy
   • DAn acid

   (b)

   The manufacturer explains to customers that stainless steel cutlery is much harder and more resistant to scratching than cutlery made from pure iron. What is the main reason alloys such as stainless steel are generally harder and stronger than the pure metals they are made from?

   [1 mark]

   • AAlloys always have lower melting points than pure metals
   • BAlloys contain no metallic bonding
   • CAlloys have a lower density than pure metals
   • DThe different sized atoms in the alloy disrupt the regular layers, making it harder for layers of atoms to slide over each other

   (c)

   State two properties of stainless steel, other than hardness, that make it suitable for use in cutlery.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A brass instrument maker mixes copper with zinc to produce brass for trumpets and trombones, rather than using pure copper, because the resulting alloy is stronger and holds its shape better under the stresses of manufacture.

   (a)

   What two metals are mixed to form brass?

   [1 mark]

   • AIron and chromium
   • BIron and carbon
   • CCopper and zinc
   • DAluminium and copper

   (b)

   The instrument maker notices that pure copper is soft and easily dented, but brass keeps its shape well. In terms of atomic structure, why does adding zinc atoms to copper make the resulting alloy harder than pure copper?

   [1 mark]

   • AZinc atoms remove the metallic bonding from the structure
   • BZinc atoms are a different size from copper atoms, disrupting the regular layers of atoms and preventing them from sliding over each other easily
   • CZinc atoms are exactly the same size as copper atoms, so the layers slide even more easily
   • DZinc atoms turn the alloy into an ionic compound

   (c)

   Explain, in terms of structure, why brass is harder than pure copper.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A civil engineer is comparing pure iron with steel (an alloy of iron and carbon) for use in the frame of a new bridge.

   (a)

   Explain why steel is a more suitable material for the bridge frame than pure iron, referring to the general properties of alloys compared with pure metals.

   [3 marks]

   (b)

   The engineer also considers using stainless steel, rather than ordinary carbon steel, for parts of the bridge exposed to rain and sea spray. Describe, in terms of composition and properties, why stainless steel would be more suitable than ordinary steel for these exposed parts, and explain in terms of structure why alloys such as stainless steel are harder than the pure metals from which they are made.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A metallurgy student is asked to explain, for a general audience, why alloys such as brass and stainless steel are more useful than the pure metals from which they are made.

   (a)

   Describe what an alloy is, using brass and stainless steel as examples, and explain in terms of atomic structure why alloys are generally harder and stronger than pure metals.

   [6 marks]

   (b)

   The same student is then asked to apply this understanding to a specific design problem: choosing materials for a set of surgical instruments that must be extremely hard, resistant to corrosion from bodily fluids, and able to hold a sharp edge. Explain why an alloy such as stainless steel would be a better choice than a pure metal for this application, and describe the properties that make it suitable.

   [6 marks]

   Total for question 4: 12 marks

End of questions