Question 1: Giant covalent structures consist of atoms bonded together by covalent bonds in a continuous network that extends throughout the material. Examples include diamond, graphite, and silicon dioxide. These structures exhibit unique properties such as high melting points, hardness, and insolubility.

Answer: Giant covalent structures are networks of atoms bonded by covalent bonds that form a continuous, extensive structure, resulting in distinctive properties like high melting points and hardness.

Question 1: Define a giant covalent structure.

Answer: A large network of atoms bonded covalently in a continuous structure extending throughout the material.

Question 2: Explain why diamond has a high melting point.

Answer: Because it has strong covalent bonds in a giant network that require a lot of energy to break.

Question 3: Describe the difference in electrical conductivity between diamond and graphite.

Answer: Diamond does not conduct electricity due to lack of free electrons, while graphite conducts because of delocalised electrons within its layers.

Question 1: Calculate the energy needed to melt 50 grams of diamond, given that the molar heat of fusion for diamond is approximately 1.9 kJ/mol. (Atomic mass of carbon = 12 g/mol)

Answer: Energy = (mass / molar mass) × heat of fusion = (50 / 12) mol × 1.9 kJ/mol ≈ 7.92 kJ

Question 1: Identify two variables you would control in an experiment testing the thermal stability of silicon dioxide and suggest safety precautions.

Answer: Variables: temperature and purity of silicon dioxide; Safety precautions: wear heat-resistant gloves and eye protection.

Question 1: A sample of a giant covalent structure has a melting point of over 3500°C and is insoluble in water. Based on this data, which structure is most likely, diamond or graphite? Explain your reasoning.

Answer: Most likely diamond, because its very high melting point and insolubility suggest a strong covalent network characteristic of diamond.

Question 1: Explain how the structure of diamond accounts for its properties such as hardness, high melting point, and lack of electrical conductivity. Include in your answer the type of bonding, the arrangement of atoms, and the implications for its uses in industry.

Answer: Diamond has a three-dimensional network of carbon atoms bonded covalently in a tetrahedral arrangement, forming a rigid and strong structure. These covalent bonds require a lot of energy to break, giving diamond its hardness and high melting point. The absence of free electrons means it does not conduct electricity. Its properties make it ideal for cutting tools and industrial abrasives.

Question 1: Discuss one industrial application of graphene, a form of giant covalent structure, and explain how its properties make it suitable for this use.

Answer: Graphene is used in high-speed electronic devices because of its excellent electrical conductivity, flexibility, and strength, which enable faster data transmission and durable flexible electronics.