// FIELD GUIDE 13 — LEVEL L3 (GCSE / NATIONAL 5)
Quantitative chemistry: the mole
Atoms are too small and too numerous to count one by one — so chemists count them in batches of 6.02 × 10²³, called a mole. It's just a chemist's "dozen," scaled up enormously.
// FIG. 01 — MASS ↔ MOLES CALCULATOR
MOLAR MASS (M)
{{ molarMass }} g/mol
→
MOLES (n = m/M)
{{ moles }} mol
{{ particleCount }}
// L3 — MOLAR MASS
The molar mass (M) of a substance — in grams per mole — is just its relative formula mass read off the periodic table. Water (H₂O) is (2×1) + 16 = 18 g/mol, so 18 g of water is exactly one mole of it: 6.02 × 10²³ molecules.
// L3 — WHY BOTHER WITH MOLES?
Reactions happen atom-for-atom, molecule-for-molecule — not gram-for-gram. Converting mass to moles lets you use a balanced equation directly: if 2 moles of hydrogen react with 1 mole of oxygen, you now know exactly what mass of each you need, no matter how big or small the reaction.
// REFERENCES & FURTHER READING
Cross-check against your own exam board's specification (AQA, Edexcel, OCR, SQA).