Edexcel GCSE Chemistry: Bonding, Structure and Properties

Diamond and graphite are both giant covalent structures made only of carbon atoms, yet their properties are very different.

• Diamond is extremely hard and does not conduct electricity.
• Graphite is soft and slippery and does conduct electricity.
• Both have very high melting points.

Explain, in terms of their structure and bonding, why diamond and graphite have these different properties but both have very high melting points. (6 marks)

Sodium chloride (NaCl) is an ionic compound with a giant ionic lattice.

(a) Explain why solid sodium chloride does not conduct electricity, but molten sodium chloride does. (2 marks)

(b) Explain why sodium chloride has a high melting point. (2 marks)

Metals such as copper are good electrical conductors and can be bent into shape (they are malleable). Metals have a giant metallic structure.

(a) Describe the structure and bonding in a metal such as copper. (2 marks)

(b) Explain why metals are able to conduct electricity. (1 mark)

Nanoparticles are tiny particles with dimensions of roughly 1–100 nm. As particles get smaller, their surface area to volume ratio increases. This makes nanoparticles useful as catalysts and in sun creams, but it also raises safety concerns.

Consider a cube-shaped particle of side length $10\ \text{nm}$10 nm.

(a) A cube has 6 faces. Calculate the surface area to volume ratio of this cube. Show your working. (2 marks)

(b) State one reason why a high surface area to volume ratio makes nanoparticles useful as catalysts. (1 mark)

Carbon dioxide ($CO_2$CO2​) is a simple molecular substance and is a gas at room temperature. The covalent bonds within each $CO_2$CO2​ molecule are very strong.

Explain why carbon dioxide has a low boiling point, even though the covalent bonds within its molecules are strong. (2 marks)

Graphene is a form (allotrope) of carbon.

State how many carbon atoms each carbon is covalently bonded to in graphene. (1 mark)