AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
One mole of a substance contains the same number of the stated particles,…
Full specification wording
Moles (HT only): One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance.
A mole is a fixed amount of particles, just as a dozen is a fixed count.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 6
Study notes
From the checked teaching notes for this specification point.
The idea
A mole is a fixed amount of particles, just as a dozen is a fixed count. One mole of any substance contains the same number of stated particles, whether those particles are atoms, molecules, ions or electrons. For example, one mole of helium contains the same number of atoms as one mole of carbon, and one mole of carbon dioxide contains the same number of molecules as one mole of water. The type of particle must be stated because the same amount in moles can refer to different entities. This idea allows chemists to compare amounts fairly in equations and calculations. It also explains why reacting ratios in equations correspond to simple whole-number ratios of moles.
What earns the marks
- State that one mole of any substance contains the same number of stated particles.
- Identify the stated particle correctly, such as atoms in a metal, molecules in a covalent compound or ions in an ionic compound.
- Link the concept to balanced equations, where coefficients give the ratio of moles of each substance.
Common mistakes and how to put them right
Assuming one mole of any substance has the same mass.
Put it right by stating that the number of particles is the same but the mass depends on the relative formula mass.
Mixing up the type of particle, such as saying one mole of oxygen gas contains one mole of atoms rather than one mole of O₂ molecules.
Put it right by naming the particle.
Thinking that one mole of an ionic compound contains one mole of ions.
Put it right by stating that it contains one mole of formula units, which contain the stated ions in the ratio shown by the formula.
Exam tips
- Always name the particle you are counting, for example atoms, molecules or ions.
- Use the phrase 'same number of particles' when comparing equal amounts in moles.
- When using equations, check that the coefficients are balanced before interpreting them as mole ratios.
Try the lesson
The start of the Moles (HT only): One mole of a substance contains the same number of the stated particles, atoms, molecules or ions as one mole of any other substance. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement correctly compares one mole of oxygen molecules, O₂, with one mole of carbon dioxide molecules, CO₂?
Listen
A mole is a fixed amount of particles, just as a dozen is a fixed count. One mole of any substance contains the same number of stated particles, whether those particles are atoms, molecules, ions or electrons. For example, one mole of helium contains the same number of atoms as one mole of carbon, and one mole of carbon dioxide contains the same number of molecules as one mole of water. The type of particle must be stated because the same amount in moles can refer to different entities. This idea allows chemists to compare amounts fairly in equations and calculations. It also explains why reacting ratios in equations correspond to simple whole-number ratios of moles. A strong answer earns marks for these points. State that one mole of any substance contains the same number of stated particles. Identify the stated particle correctly, such as atoms in a metal, molecules in a covalent compound or ions in an ionic compound. Use the idea to compare amounts of different substances in moles, for example equal moles of two molecular gases contain equal numbers of molecules, or equal moles of any two substances contain equal numbers of their stated particles. Link the concept to balanced equations, where coefficients give the ratio of moles of each substance. A common slip: Assuming one mole of any substance has the same mass. Instead, stating that the number of particles is the same but the mass depends on the relative formula mass. Exam tip: Always name the particle you are counting, for example atoms, molecules or ions.
See it
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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