A student states: 'One mole of carbon atoms and one mole of water molecules both contain the same number of particles.' Explain why the student is correct and state the name given to this number of particles.

Cambridge International IGCSE Chemistry (0620) — 3.3 The mole and the Avogadro constant · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

One mole of any substance always contains the same number of particles.
The number of particles in one mole is approximately 6.02 × 10²³.
This number is called the Avogadro constant (or Avogadro's number).
The particles referred to differ between substances – carbon contains atoms whereas water contains molecules.

Examiner tips

  • Use the exact phrase "same number of particles" to show understanding of the mole concept.
  • State the numerical value 6.02×10²³ and the term Avogadro constant.
  • Explain the difference in particle type (atoms vs molecules).

Common mistakes

  • Confusing Avogadro constant with molar mass.
  • Saying the same number of particles without mentioning the value 6.02×10²³.
  • Not distinguishing between atoms and molecules.

Mark scheme (4 marks)

  1. One mole of any substance always contains the same number of particles
  2. The number of particles in one mole is approximately 6.02 × 10²³
  3. This number is called the Avogadro constant (or Avogadro's number)
  4. The particles referred to differ between substances — carbon contains atoms whereas water contains molecules

Key terms in this question

mole · particles

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