1. 1
   A technician is investigating a sample of scrap metal collected from an old factory. The sample contains iron, and the technician notes that a compound scraped from its surface is orange-brown in colour. The technician also observes that a powdered form of the same metal is used elsewhere in the factory as a catalyst in a large-scale industrial reaction.

   (a)

   Which property is typical of transition metals such as iron and copper?

   [1 mark]

   • ALow melting point
   • BHigh density
   • CLow density
   • DPoor catalytic activity

   (b)

   The orange-brown compound found on the surface of the iron sample is most likely to be an example of which of the following?

   [1 mark]

   • AA coloured compound formed because iron is a transition metal
   • BA pure sample of iron metal
   • CAn alloy of iron and carbon
   • DA noble gas compound

   (c)

   State the process by which the orange-brown compound formed on the iron sample, and name two substances from the environment that must both be present for this process to occur.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A ship's steel hull is fitted with several blocks of magnesium bolted directly onto its outer surface, below the waterline. Over several months of being at sea, the engineers observe that the magnesium blocks gradually corrode away, while the steel hull underneath remains largely undamaged. The engineers plan to replace the magnesium blocks periodically as part of routine maintenance.

   (a)

   Which method is being used to protect the ship's hull in this situation?

   [1 mark]

   • APainting
   • BGalvanising
   • CSacrificial protection
   • DOiling

   (b)

   Why does the magnesium corrode instead of the steel hull?

   [1 mark]

   • AMagnesium is less reactive than iron, so it protects the hull
   • BMagnesium reacts only with oxygen, never with water
   • CMagnesium physically blocks water from reaching the hull
   • DMagnesium is more reactive than iron, so it reacts in preference to the hull

   (c)

   Describe two other methods, besides sacrificial protection, that could be used to prevent the steel hull from rusting, explaining how each method works.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A jeweller melts together 750 parts by mass of pure gold with 250 parts by mass of copper to make a ring that looks like gold but is much harder-wearing. A separate manufacturer produces steel for bridge cables by alloying iron with small amounts of carbon and other metals.

   (a)

   Explain, using ideas about the structure of metals, why this gold-copper alloy is harder than pure gold.

   [3 marks]

   (b)

   A separate manufacturer produces steel for use in bridge cables by alloying iron with small amounts of carbon and other metals. Explain why iron is alloyed to produce alloy steels rather than being used in its pure form for this application, and suggest why the amount of carbon added must be carefully controlled.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A company manufactures decorative cutlery from a base metal and wants to give the items the appearance of silver while also improving their resistance to corrosion. The company considers electroplating the cutlery with a thin layer of silver, using an electrolytic cell in which the cutlery forms one electrode, a bar of pure silver forms the other electrode, and both are immersed in a solution containing silver ions.

   (a)

   Explain, in detail, how this electroplating process works, including the role of each electrode and the movement of ions and electrons, and discuss the benefits it provides to the cutlery.

   [6 marks]

   (b)

   The same company also manufactures electrical wiring and cooking pans, and must choose suitable metals for each product based on their properties. Evaluate why copper is chosen for electrical wiring while aluminium, rather than copper, is often chosen for large overhead power cables, and why aluminium alloys such as magnalium are chosen for cooking pans and other lightweight items, relating each choice to the properties of the metals involved.

   [6 marks]

   Total for question 4: 12 marks

End of questions