1. 1
   An electrician chooses copper wire, rather than iron wire, to carry electricity through the walls of a new house, because copper is a much better conductor of electricity. The electrician also needs to bend the copper wire carefully around corners inside the wall cavities.

   (a)

   Which statement correctly explains why copper is so widely used for electrical wiring?

   [1 mark]

   • ACopper is an excellent conductor of electricity, allowing current to flow through it with very little resistance
   • BCopper is chosen because it is a poor conductor of electricity, which makes the wiring safer
   • CCopper is used because it dissolves easily in water, allowing electricity to pass through it
   • DCopper is chosen because it is the lightest of all known metals

   (b)

   The electrician also needs to bend the copper wire carefully around corners inside the wall cavities without it snapping. Which statement explains why copper can be bent into shape like this?

   [1 mark]

   • ACopper reacts with the air to form a flexible new compound
   • BCopper is a liquid at room temperature, allowing it to flow around corners
   • CCopper contains no metallic bonding, so it can be reshaped freely
   • DCopper is malleable, meaning the layers of atoms in its structure can slide over each other while remaining held together

   (c)

   Explain why copper is such a suitable material for electrical wiring in houses, referring to both its electrical properties and its ability to be shaped during installation.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A plumber installs copper pipes to carry hot water around a house, rather than using pipes made from a highly reactive metal. The pipes must also be bent around corners in the wall to reach different rooms, and must be hard enough to keep their shape once installed.

   (a)

   Which statement best explains why copper is a suitable choice of metal for water pipes?

   [1 mark]

   • ACopper reacts vigorously with water, which helps keep the pipes clean
   • BCopper does not react with water, so the pipes do not corrode or contaminate the water supply over time
   • CCopper dissolves slowly in water, releasing useful minerals into the water supply
   • DCopper melts at a very low temperature, making it easy to join pipe sections together

   (b)

   The copper pipes must also be bent around corners in the wall to reach different rooms, yet must remain hard enough to keep their shape once installed and not be easily dented. Which statement best describes this combination of properties in copper?

   [1 mark]

   • ACopper is too brittle to be bent into shape without cracking
   • BCopper is so soft that it constantly changes shape after installation
   • CCopper can be bent into shape during installation, but is hard enough afterwards to hold its shape and resist everyday knocks
   • DCopper cannot be shaped at all and must be cast directly into the required form

   (c)

   Explain why copper, rather than a highly reactive metal, is used to make water pipes and tanks, and why copper can be bent to fit around corners while still being hard enough to keep its shape once installed.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A homeowner is comparing copper pipes with pipes made from sodium, a highly reactive metal, for a new plumbing system, even though sodium is never actually used for this purpose in practice. The homeowner also wants to understand why copper, rather than a very hard, unreactive giant covalent substance, is used instead.

   (a)

   Explain why sodium would be completely unsuitable for water pipes, in contrast to copper.

   [3 marks]

   (b)

   The homeowner also wonders why copper, rather than an extremely hard, unreactive giant covalent substance such as silicon dioxide, is used to make water pipes, given that silicon dioxide also does not react with water. Explain why copper, rather than a giant covalent substance, is the more practical choice for making pipes that must be shaped and joined together.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A heating engineer is designing a domestic hot water cylinder that must conduct heat efficiently from an internal heating element to the surrounding water, be bent and shaped into a cylindrical tank during manufacturing, and resist corrosion from the water it holds for many years. The engineer also considers, but rejects, using a plastic material for the same cylinder.

   (a)

   Describe, in terms of its properties, why copper is an excellent choice of material for this hot water cylinder.

   [6 marks]

   (b)

   The engineer also considers using a plastic material instead of copper for parts of the hot water cylinder, since plastic is cheaper and also does not react with water. Explain why plastic would not be as suitable as copper for the parts of the cylinder that must conduct heat efficiently from the heating element to the water, even though plastic shares copper's resistance to reacting with water.

   [6 marks]

   Total for question 4: 12 marks

End of questions