Question 1
Which charged particles carry current in molten sodium chloride?
Need a hint for Question 1?
Ionic conduction involves movement of ions.
Check Question 1
Mobile sodium and chloride ions.
STUDENT SPACE · TOPIC 6
Ionic and molecular properties
Use structure, attractions and mobile charged particles to explain properties.
The essentials
- Ionic lattices have high melting points because much energy is needed to overcome strong electrostatic attractions.
- Ionic substances conduct when molten or dissolved because their ions can move. Solid ions stay in fixed positions.
- Simple molecular substances usually have low melting and boiling points because intermolecular forces are weak. Melting does not break their covalent bonds.
Key vocabulary
| English | Chinese |
|---|---|
| intermolecular force | 分子间作用力 |
| molten | 熔融的 |
| mobile ion | 可移动离子 |
Quick practice
Try each question before opening its hint or answer. Use paper for calculations and diagrams.
Question 2
Explain why solid MgO cannot conduct but molten MgO can.
Need a hint for Question 2?
Conduction needs charged particles that can move.
Check Question 2
In solid MgO the ions are fixed. In molten MgO the ions are mobile and carry charge.
Question 3
Water boils without breaking its O–H covalent bonds. Explain what is overcome.
Need a hint for Question 3?
Distinguish attractions between molecules from bonds within them.
Check Question 3
Intermolecular forces between water molecules are overcome.
Use the matching chapter worksheet. Attempt independently, compare your reasoning with your partner, then bring unresolved questions to your teacher.
PREDICT · TRY · EXPLAIN · 3–5 MINUTES
Ions, lattices and conductivity
Predict which states conduct. Change the state, then explain what carries charge.
1 · Form the ions
Na has electron arrangement 2,8,1. Cl has 2,8,7.
Na (2,8,1) → e⁻ → Cl (2,8,7)
Predict the charge on each atom after the transfer.
2 · Test conductivity
Na⁺Cl⁻Na⁺Cl⁻Na⁺Cl⁻Cl⁻Na⁺Cl⁻Na⁺Cl⁻Na⁺Na⁺Cl⁻Na⁺Cl⁻Na⁺Cl⁻
Predict: can charged particles move through this sample?
Molten salt is melted; aqueous salt is dissolved in water. These are different processes. This schematic shows mobility, not a full electrolysis circuit.