Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want the mole — linking mass, particles and chemical amounts — to become a reliable source of marks instead of a formula-memorising exercise.
What query it owns: how to understand and revise the mole in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the the-mole revision-guide angle, while Tutopiya’s The Mole subtopic page owns the learning resource and the free The Mole quiz owns the practice.

The mole is the chemist’s counting unit. Cambridge IGCSE Coordinated Science (0654) expects you to convert between mass, moles and number of particles, use relative atomic and formula masses, and apply mole ratios in simple stoichiometry. This guide links each idea to what examiners reward, so you can tackle calculation and definition questions with confidence.

Key takeaways

• One mole contains 6.02 × 10²³ particles (Avogadro’s constant).
• Relative atomic mass (Aᵣ) has no units; molar mass is in g/mol.
• Moles = mass ÷ molar mass (n = m/M).
• Number of particles = moles × 6.02 × 10²³.
• Mole ratios from balanced equations link amounts of reactants and products.

What is the mole in Cambridge IGCSE Coordinated Science?

The mole lets you count particles by weighing. Because atoms are too small to count individually, chemists use a standard amount — one mole — equal to Avogadro’s number of particles. The molar mass of a substance (in g/mol) numerically equals its relative formula mass, so a weighed sample tells you how many moles you have.

You can read the full explanation, worked examples and notes on Tutopiya’s The Mole subtopic page before you attempt questions.

Core formulas and relationships

Quantity	Formula	Units
Moles from mass	n = m / M	mol = g ÷ (g/mol)
Mass from moles	m = n × M	g = mol × (g/mol)
Particles from moles	N = n × 6.02 × 10²³	particles
Molar mass	Sum of Aᵣ values in formula	g/mol

Relative mass — what examiners expect

Term	Meaning	Example
Relative atomic mass (Aᵣ)	Average mass of an atom relative to ¹⁄₁₂ of carbon-12	Aᵣ(C) = 12
Relative formula mass (Mᵣ)	Sum of Aᵣ values in a formula	Mᵣ(H₂O) = 18
Molar mass	Mass of one mole	H₂O = 18 g/mol

The mole in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical mole stem
Calculate	Use n = m/M or mole ratios	”Calculate the number of moles in 8 g of oxygen gas.”
State	Short definition or value	”State the value of Avogadro’s constant.”
Deduce	Work out from given data	”Deduce the mass of 0.5 mol of CO₂.”
Use mole ratio	Apply balanced equation	”How many moles of H₂O form from 2 mol of H₂?”

Worked exam-style stems (how to answer the wording)

1. “Calculate the number of moles in 9 g of water (Mᵣ = 18).” n = m/M = 9/18 = 0.5 mol. Mark-scheme reward: correct substitution and answer with unit.
2. “State the number of particles in 1 mol of any substance.” 6.02 × 10²³ particles. Reward: correct value and idea of particles.
3. “From the equation 2H₂ + O₂ → 2H₂O, how many moles of water form from 3 mol of hydrogen?” Mole ratio H₂:H₂O = 2:2 = 1:1, so 3 mol of water. Reward: correct ratio applied.

Test yourself with the The Mole quiz once you can convert between mass, moles and particles without a formula sheet.

How the mole connects to the rest of Coordinated Science chemistry

The mole underpins stoichiometry — reacting masses, limiting reagents and percentage yield. It builds on atomic structure and formula writing. The Cambridge IGCSE Coordinated Science resource hub links every Stoichiometry subtopic.

Common mistakes students make

• Confusing relative formula mass (no unit) with molar mass (g/mol).
• Using molecular mass for ionic compounds (use formula mass).
• Forgetting to convert mass to grams before dividing by molar mass.
• Mixing up mole ratio with mass ratio in equations.
• Rounding 6.02 × 10²³ incorrectly in multi-step calculations.

When you need more support

If mole calculations keep costing marks, work through the The Mole quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is the mole hard in Coordinated Science? The concepts are straightforward once you practise n = m/M and mole ratios from balanced equations.

What is Avogadro’s constant? The number of particles in one mole: 6.02 × 10²³ mol⁻¹.

How do I find molar mass? Add the relative atomic masses of all atoms in the formula; the result is the molar mass in g/mol.

How do I revise the mole effectively? Practise mass-to-mole and mole-to-particle conversions, then apply mole ratios from equations before taking the quiz.

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