The Mole Concept: Introduction

50 lessons, pages 721–770.

  1. Why Chemists Need to Count Particles — Equations speak in particles, laboratories work in grams
  2. Counting by Weighing — How shops count nails and coins without counting them one by one
  3. Counting Units: Pairs, Dozens and Reams — Grouping units that make large numbers manageable
  4. Just How Small Is an Atom? — Why a single atom is far too light to weigh directly
  5. The Mole: The Chemist's Counting Unit — Definition of the mole as an SI base unit
  6. The Avogadro Constant — 6.022 × 10²³ particles per mole and its unit mol⁻¹
  7. How Big Is 6.022 × 10²³? — Picturing Avogadro's number with everyday comparisons
  8. Standard Form for Very Large and Very Small Numbers — Writing, multiplying and dividing powers of ten
  9. Amedeo Avogadro and the History of the Mole — From gas volumes to a fixed defined constant
  10. Specifying the Particles: Atoms, Molecules, Ions and Formula Units — Why 'one mole of oxygen' is ambiguous
  11. Moles to Number of Particles — N = n × Nₐ in simple one-step calculations
  12. Number of Particles to Moles — n = N ÷ Nₐ and sensible rounding
  13. Counting Atoms Inside Molecules — Using subscripts to find moles of each atom in a compound
  14. Counting Ions in Ionic Compounds — Moles of ions produced from one mole of a formula unit
  15. Relative Atomic Mass Revisited — The carbon-12 scale and weighted average masses of isotopes
  16. Reading Relative Atomic Masses from the Periodic Table — Choosing and rounding Aᵣ values for calculations
  17. Relative Formula Mass of Molecules — Adding Aᵣ values to find Mᵣ of covalent substances
  18. Relative Formula Mass of Ionic Compounds — Formula units, brackets and multiplying out groups
  19. Relative Formula Mass of Hydrated Salts — Including water of crystallisation in Mᵣ
  20. Molar Mass: Grams per Mole — Linking Mᵣ to M in g mol⁻¹
  21. Why Molar Mass Equals Relative Mass in Grams — How the Avogadro constant bridges atomic mass units and grams
  22. Molar Masses of Elements and Diatomic Molecules — O versus O₂, Cl versus Cl₂ and why it matters
  23. The Mass–Moles Relationship — n = m ÷ M and the formula triangle
  24. Converting Mass to Moles — Step-by-step method with units at every stage
  25. Converting Moles to Mass — m = n × M for elements and compounds
  26. Finding Molar Mass from Mass and Moles — M = m ÷ n and identifying an unknown substance
  27. Working with Kilograms, Milligrams and Tonnes — Unit conversions before and after mole calculations
  28. Significant Figures in Mole Calculations — Matching precision of answers to the data given
  29. Mass to Number of Particles — Two-step route through moles
  30. Number of Particles to Mass — Reversing the route: particles to moles to grams
  31. The Mass of a Single Atom or Molecule — Dividing molar mass by the Avogadro constant
  32. Mass of an Element Within a Compound — Using moles and formulae to find the mass of one element present
  33. Percentage by Mass of an Element — Composition from the formula and molar mass
  34. Percentage of Water in a Hydrated Salt — Applying percentage composition to crystals
  35. Comparing Amounts: Equal Masses, Different Moles — Why 1 g of hydrogen contains more particles than 1 g of lead
  36. Comparing Amounts: Equal Moles, Different Masses — Same number of particles, different weights
  37. Moles in Chemical Equations — Reading coefficients as mole ratios
  38. Conservation of Mass Seen Through Moles — Checking that reactant and product masses balance
  39. Simple Reacting Mass Calculations — Mass to moles, mole ratio, moles to mass
  40. Moles in Everyday Life: Food, Medicine and Fuel — Doses, nutrients and combustion counted in moles
  41. Moles in Industry and the Environment — Scaling up to tonnes and tracking pollutants
  42. Measuring Amounts Safely in the Laboratory — Balances, weighing technique, uncertainty and safe handling
  43. Exploring Moles with the Mole Simulator — Interactive links between mass, moles and particle count
  44. Common Mistakes in Mole Calculations — Wrong particle type, unit slips and inverted formulae
  45. Checking Answers for Reasonableness — Estimation and order-of-magnitude checks
  46. Multi-Step Mole Problems — Planning a route through mass, moles and particles
  47. Mole Calculations in Exam Questions — Command words, layout and earning method marks
  48. The Mole Beyond the Basics — A preview of gas volumes, concentrations and empirical formulae
  49. Mixed Practice: Avogadro Constant, Molar Mass and Moles — Graded problems drawing the whole unit together
  50. The Mole Concept: Unit Review — Key ideas, formulae and connections across the unit