AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
These substances do not conduct electricity because the molecules do not…
Full specification wording
Properties of small molecules: These substances do not conduct electricity because the molecules do not have an overall electric charge.
Simple molecular substances do not conduct electricity because their molecules are neutral overall.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 4 of 5
Study notes
From the checked teaching notes for this specification point.
The idea
Simple molecular substances do not conduct electricity because their molecules are neutral overall. Each molecule contains covalent bonds in which electrons are shared between atoms, but the molecule as a whole has no net electric charge. Since there are no charged particles that are free to move, no current can flow. This applies whether the substance is solid, liquid or gaseous.
For example: Methane (CH₄) and water (H₂O) are simple molecular substances and do not conduct electricity, unlike ionic compounds when molten or dissolved, or metals, which contain free electrons.
What earns the marks
- Simple molecular substances contain molecules that are electrically neutral overall.
- Covalent bonds involve shared electrons, but this sharing does not give the molecule a net charge.
- Electrical conduction requires charged particles that are free to move.
- Because simple molecular substances have no free charged particles, they do not conduct electricity.
- The absence of conduction applies in solid, liquid and gaseous states.
- A contrast with ionic or metallic conductors can be used to show why simple molecular substances behave differently.
Common mistakes and how to put them right
Thinking that shared electrons in covalent bonds can carry charge through the substance.
Put it right by stating that the electrons are localised within the molecule and the molecule is neutral overall.
Assuming that a simple molecular substance will conduct when melted.
Put it right by explaining that melting overcomes intermolecular forces but does not produce free charged particles.
Confusing simple molecular substances with ionic compounds.
Put it right by noting that ionic compounds can conduct when molten or dissolved because their ions are free to move.
Exam tips
- State clearly that conduction needs charged particles that are free to move.
- Explain that simple molecular substances have no overall charge and no free charged particles.
- Use a named example, such as methane or water, and contrast it with an ionic or metallic conductor.
Try the lesson
The start of the Properties of small molecules: These substances do not conduct electricity because the molecules do not have an overall electric charge. lesson, made from checked teaching notes for this specification point.
Have a go first
A simple molecular substance such as methane is tested with a circuit containing a battery and a lamp. What is observed, and why?
Listen
Simple molecular substances do not conduct electricity because their molecules are neutral overall. Each molecule contains covalent bonds in which electrons are shared between atoms, but the molecule as a whole has no net electric charge. Since there are no charged particles that are free to move, no current can flow. This applies whether the substance is solid, liquid or gaseous. For example, methane (CH₄) and water (H₂O) are simple molecular substances and do not conduct electricity, unlike ionic compounds when molten or dissolved, or metals, which contain free electrons. A strong answer earns marks for these points. Simple molecular substances contain molecules that are electrically neutral overall. Covalent bonds involve shared electrons, but this sharing does not give the molecule a net charge. Electrical conduction requires charged particles that are free to move. Because simple molecular substances have no free charged particles, they do not conduct electricity. A common slip: Thinking that shared electrons in covalent bonds can carry charge through the substance. Instead, stating that the electrons are localised within the molecule and the molecule is neutral overall. Exam tip: State clearly that conduction needs charged particles that are free to move.
See it
Label the diagram
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1Box 1
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3Box 3
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