1. 1
   A pencil manufacturer uses graphite, a form of carbon, as the writing core of its pencils, and compares it with diamond, another form of carbon used in cutting tool tips.

   (a)

   In graphite, each carbon atom is covalently bonded to three other carbon atoms, forming flat layers. What type of giant structure does graphite have?

   [1 mark]

   • AA giant covalent structure
   • BA giant ionic lattice
   • CA simple molecular structure
   • DA metallic lattice

   (b)

   The manufacturer notes that graphite feels slippery and its layers easily slide over one another, allowing it to leave marks on paper. Which feature of graphite's structure explains this property?

   [1 mark]

   • AGraphite's layers are joined by strong ionic bonds that allow easy sliding
   • BGraphite has no covalent bonds at all, so the atoms slide freely
   • CThe layers of carbon atoms are held together only by weak forces between layers, allowing them to slide over each other easily
   • DGraphite consists of small individual molecules that roll over each other

   (c)

   Explain why graphite is able to conduct electricity, even though it is a form of carbon, a non-metal.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A jeweller sets a diamond, another giant covalent structure of carbon, into a cutting tool used to cut glass, taking advantage of diamond's extreme hardness, in contrast to graphite's softness.

   (a)

   In diamond, each carbon atom is covalently bonded to how many other carbon atoms?

   [1 mark]

   • AThree
   • BFour
   • CTwo
   • DSix

   (b)

   Diamond is extremely hard and has a very high melting point. Which feature of its structure best explains this?

   [1 mark]

   • ADiamond's layers can slide over each other easily, giving it strength
   • BDiamond consists of separate small molecules held together by weak intermolecular forces
   • CDiamond's carbon atoms are held together by delocalised electrons in a metallic lattice
   • DEvery carbon atom is joined to four others by strong covalent bonds extending rigidly throughout the whole three-dimensional structure

   (c)

   Explain why diamond does not conduct electricity, unlike graphite.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A furnace engineer selects silicon(IV) oxide, SiO2, to line the inside of an industrial furnace because it can withstand extremely high temperatures without melting, and compares its behaviour with diamond.

   (a)

   Describe the structure of silicon(IV) oxide in terms of the bonding between silicon and oxygen atoms.

   [3 marks]

   (b)

   Explain why silicon(IV) oxide, like diamond, has a very high melting point and does not conduct electricity, relating your answer to the similarities in structure and bonding between the two substances.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A metallurgical company is designing a set of electrical contacts and needs a material that is both an excellent electrical conductor and can also withstand extremely high temperatures without melting. An engineer proposes graphite as a candidate, since it conducts electricity well and does not melt easily, while also considering copper, a metal, as an alternative.

   (a)

   Explain fully, in terms of structure and bonding, why graphite is able to conduct electricity and has a very high melting point, comparing this with the bonding found in a typical metal such as copper.

   [6 marks]

   (b)

   A different engineer on the same project suggests using diamond instead of graphite for a separate component that must be an excellent electrical insulator but also extremely hard and resistant to wear. Explain fully, in terms of structure and bonding, why diamond is an excellent electrical insulator and extremely hard, and explain why diamond would not be suitable if electrical conductivity were also required, contrasting this with graphite's properties.

   [6 marks]

   Total for question 4: 12 marks

End of questions