Question 1: Define a giant covalent structure and explain how it differs from simple covalent molecules.

Answer: A giant covalent structure is a large, continuous network of atoms bonded together by covalent bonds, forming a single massive molecule. Unlike simple covalent molecules, which are discrete and held together by intermolecular forces, giant covalent structures have extensive covalent bonding throughout, resulting in unique properties such as high melting points and hardness.

Question 2: List three common examples of giant covalent structures.

Answer: Diamond, graphite, silica (silicon dioxide).

Question 3: Describe the main difference in bonding between diamond and graphite.

Answer: In diamond, each carbon atom forms four strong covalent bonds in a tetrahedral structure, making it very hard. In graphite, each carbon atom forms three covalent bonds in hexagonal layers, with weak forces between layers, allowing them to slide over each other.

Question 4: Explain why giant covalent structures generally have high melting points.

Answer: Because of the extensive covalent bonds throughout the structure, a large amount of energy is required to break these bonds and change the state from solid to liquid.

Question 1: Compare the electrical conductivity of diamond and graphite, providing reasons for their differences.

Answer: Diamond does not conduct electricity because all electrons are involved in covalent bonds, leaving no free electrons. Graphite conducts electricity because each carbon atom has one delocalised electron that can move freely between layers.

Question 2: Describe the hardness of diamond and explain the reason for its hardness.

Answer: Diamond is extremely hard due to its rigid, three-dimensional network of covalent bonds that resist external forces.

Question 3: Why are giant covalent substances generally insoluble in water?

Answer: Because of the strong covalent bonds throughout the structure, they do not break apart in water; thus, they are insoluble.

Question 1: Calculate the amount of energy (in kJ) required to break all covalent bonds in one mole of diamond, given that each carbon-carbon bond requires 355 kJ to break and each carbon atom forms four bonds.

Answer: Energy required = 4 bonds per carbon atom × 355 kJ per bond = 1420 kJ per atom. For one mole (6.022×10^23 atoms), energy = 1420 kJ × 6.022×10^23 = approximately 8.55×10^26 kJ.

Question 1: Identify one industry where diamond is used and explain why its properties make it suitable for this purpose.

Answer: Diamond is used in cutting tools and jewellery because of its hardness and durability.

Question 2: Suggest two reasons why graphite is suitable as a lubricant in machinery.

Answer: Because layers can slide over each other easily due to weak interlayer forces, and it is stable at high temperatures.

Question 3: Discuss a potential technological advancement that could utilise the unique properties of giant covalent structures.

Answer: Advances in nanotechnology could utilise the exceptional strength and thermal conductivity of diamond to develop ultra-hard materials, improved heat sinks for electronics, or quantum computing components using diamond-based quantum bits (qubits).