What mistakes do students make with Properties of ionic compounds?

Saying that electrons carry charge in ionic solutions. Ions are the charge carriers. Believing that solid ionic compounds conduct because they contain ions. The ions must be free to move. Confusing melting with dissolving. Both processes free the ions, but melting produces a liquid and dissolving produces an aqueous solution.

What are the exam tips for Properties of ionic compounds in Chemistry AQA GCSE?

Always mention that ions must be free to move for conduction to occur. Use the term 'electrolyte' for a molten or aqueous ionic compound that conducts electricity. If asked to explain, refer to the movement of ions towards electrodes.

AQA · GCSE · Chemistry

Course version: 8462 · Version from Sept 2018

When melted or dissolved in water, ionic compounds conduct electricity…

Full specification wording

Properties of ionic compounds: When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.

Solid ionic compounds do not conduct electricity because the ions are fixed in the lattice and cannot move.

Checked against the AQA 8462 specification (opens in a new tab) on 21 September 2026.

Point 3 of 3

Study notes

From the checked teaching notes for this specification point.

The idea

What earns the marks

States that solid ionic compounds do not conduct electricity because ions are not free to move.
Explains that when melted or dissolved in water, the lattice breaks down and ions become mobile.
Describes how mobile ions carry charge through the liquid or solution, allowing conduction.
Uses a named example, such as molten sodium chloride or sodium chloride solution, to illustrate conduction.
Links the ability to conduct to the presence of free-moving charged particles.

Common mistakes and how to put them right

Saying that electrons carry charge in ionic solutions.
Put it right: Ions are the charge carriers.
Believing that solid ionic compounds conduct because they contain ions.
Put it right: The ions must be free to move.
Confusing melting with dissolving.
Put it right: Both processes free the ions, but melting produces a liquid and dissolving produces an aqueous solution.

Exam tips

Always mention that ions must be free to move for conduction to occur.
Use the term 'electrolyte' for a molten or aqueous ionic compound that conducts electricity.
If asked to explain, refer to the movement of ions towards electrodes.

Try the lesson

The start of the Properties of ionic compounds: When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow. lesson, made from checked teaching notes for this specification point.

Have a go first

Why can a melted ionic compound conduct electricity?

Tip: press 1 to 4 to choose

Listen

Solid ionic compounds do not conduct electricity because the ions are fixed in the lattice and cannot move. When melted or dissolved in water, the lattice breaks down and the ions become free to move. These mobile ions carry charge through the liquid or solution, so the compound conducts electricity. For example, molten sodium chloride conducts electricity, and a solution of sodium chloride in water also conducts. The ions themselves move towards the oppositely charged electrodes, completing the circuit. This explains why ionic compounds are electrolytes when molten or aqueous but insulators when solid. A strong answer earns marks for these points. States that solid ionic compounds do not conduct electricity because ions are not free to move. Explains that when melted or dissolved in water, the lattice breaks down and ions become mobile. Describes how mobile ions carry charge through the liquid or solution, allowing conduction. Uses a named example, such as molten sodium chloride or sodium chloride solution, to illustrate conduction. A common slip: Saying that electrons carry charge in ionic solutions. Instead, ions are the charge carriers. Exam tip: Always mention that ions must be free to move for conduction to occur.

See it

A top-down flowchart. At the top, 'Solid ionic compound' branches two ways. One branch leads to 'Ions fixed in the lattice and cannot move', which leads to 'Does not conduct electricity'. The other branch splits into 'Melted' and 'Dissolved in water'; both of these lead to 'Lattice breaks down and ions become free to move'. That leads to 'Mobile ions carry charge through the liquid or solution', which leads to 'Conducts electricity' and also to 'Ions move towards the oppositely charged electrodes'. — It shows why a solid ionic compound does not conduct electricity, but conducts once melted or dissolved because the ions become free to move and carry charge.

Label the diagram

Some boxes have lost their names. Pick the right name for each number.

The diagram again, with 3 boxes numbered instead of named. A top-down flowchart. At the top, 'Solid ionic compound' branches two ways. One branch leads to 'Ions fixed in the lattice and cannot move', which leads to 'Does not conduct electricity'. The other branch splits into 'Melted' and 'Dissolved in water'; both of these lead to 'Lattice breaks down and ions become free to move'. That leads to 'Mobile ions carry charge through the liquid or solution', which leads to 'Conducts electricity' and also to 'Ions move towards the oppositely charged electrodes'.

1Box 1
2Box 2
3Box 3

0 of 3 labelled

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