AQA GCSE Chemistry (8462), Higher tier · Bonding, structure and the properties of matter › Bonding, structure and properties
Practise Properties of ionic compounds. 14 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Sodium chloride is an ionic compound.
(a) Why does sodium chloride have a high melting point? Tick (✓) one box.[1]
Large amounts of energy are needed to break the many strong bonds.
Its molecules are very large.
The intermolecular forces are weak.
The ions are free to move.
(b) When does sodium chloride conduct electricity? Tick (✓) two boxes.[2]
When it is solid
When it is molten
When it is dissolved in water
Never
(c) Explain why solid sodium chloride does not conduct electricity.[1]
Show the answer and mark scheme
(a)Answer: Large amounts of energy are needed to break the many strong bonds.
(b)Answer: When it is molten; When it is dissolved in water
(c)Answer: The ions are held in fixed positions, so they cannot move to carry charge.
the ions are in fixed positions / cannot move (to carry charge)
Question 2Medium6 marks
Magnesium oxide melts at 2852 °C. Sodium chloride melts at 801 °C.
(a) Explain why magnesium oxide has a high melting point.[3]
(b) Suggest why magnesium oxide has a higher melting point than sodium chloride.[2]
(c) Magnesium oxide is used to line the inside of furnaces. Suggest why.[1]
Show the answer and mark scheme
(a)Answer: It is a giant ionic lattice with strong electrostatic forces between oppositely charged ions; lots of energy is needed to overcome them.
giant (ionic) lattice / structure
strong electrostatic forces of attraction between oppositely charged ions
a lot of energy is needed to overcome the forces / break the bonds
(b)Answer: Mg2+ and O2− ions have larger charges than Na+ and Cl− ions, so the electrostatic attraction is stronger.
the ions in magnesium oxide have larger charges (2+ and 2−) than those in sodium chloride (1+ and 1−)
so the electrostatic attraction between the ions is stronger
(c)Answer: It has a very high melting point, so it does not melt at furnace temperatures.
(very) high melting point / does not melt at high temperatures
Question 3Hard6 marks
A technician has three unlabelled white solids. One is sodium chloride, one is glucose and one is silicon dioxide.
Plan an investigation to identify each solid. Your plan should explain the expected results in terms of the structure and bonding of each substance.[6]
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Answer: Add each solid to water: silicon dioxide does not dissolve. Test the conductivity of the other two solutions: sodium chloride solution conducts (free ions), glucose solution does not (neutral molecules).
add the same mass of each solid to the same volume of water and stir
silicon dioxide does not dissolve (it is a giant covalent structure)
test the electrical conductivity of each solution using electrodes connected to a power supply and a bulb / ammeter
sodium chloride solution conducts because its ions are free to move and carry charge
glucose solution does not conduct because glucose is made of molecules with no overall charge
the solids themselves would not conduct, because the ions in solid sodium chloride are held in fixed positions
alternatively, heat small samples gently: glucose melts at a low temperature (weak forces between molecules); sodium chloride and silicon dioxide do not melt (strong bonds, high melting points)
safety: wear eye protection / switch off the power before handling the electrodes
Marked with levels of response: the full level descriptors are in the app.