Edexcel GCSE Combined Science: Chemistry: Bonding and Structure
6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Diamond and graphite are both forms (allotropes) of the element carbon. Despite being made of the same atoms, they have very different properties:
- diamond is very hard and does not conduct electricity;
- graphite is soft / slippery and does conduct electricity.
Explain, in terms of their structure and bonding, why diamond and graphite have these different properties. (6 marks)
The table gives some properties of four substances, A, B, C and D, each with a different type of structure and bonding.
| Substance | Melting point | Conducts electricity when solid? | Conducts electricity when molten/dissolved? |
|---|---|---|---|
| A | high | yes | yes |
| B | high | no | yes |
| C | low | no | no |
| D | very high | no | no |
The substances are (in no particular order): sodium chloride (ionic), copper (metallic), carbon dioxide (simple molecular), and silicon dioxide (giant covalent).
Identify which substance (A, B, C or D) is each of the four named materials, and for substance B explain why it conducts electricity only when molten or dissolved, not when solid. (4 marks)
Metals have a giant structure in which positive metal ions are arranged in a regular pattern.
(a) Describe the bonding in a metal, including what holds the structure together. (2 marks)
(b) Using your answer to part (a), explain why metals are good conductors of electricity. (1 mark)
Sodium (a metal) reacts with chlorine (a non-metal) to form the ionic compound sodium chloride.
(a) Describe what happens to the electrons when a sodium atom and a chlorine atom form ions, and give the charge on each ion formed. (2 marks)
(b) Write a balanced symbol equation, including state symbols, for sodium reacting with chlorine gas to form solid sodium chloride. (1 mark)
Carbon dioxide (CO₂) is a simple molecular substance. At room temperature it is a gas, so it has a very low boiling point.
Explain, in terms of the forces present, why carbon dioxide has a very low boiling point. (2 marks)
Poly(ethene) is a polymer made from many small ethene molecules joined together.
Name the type of small molecule that joins together to form a polymer. (1 mark)