Lesson Plan

• Apply the mole concept and Avogadro constant to convert between mass, moles, and particles.
• Determine empirical formulas from experimental mass data.
• Calculate molecular formulas using the empirical formula and a given molar mass.
• Identify common calculation pitfalls and correct rounding errors.

• Projector or interactive whiteboard
• IGCSE Chemistry textbook / handout
• Worksheet with practice problems
• Periodic table posters
• Scientific calculators
• Sample data sets for empirical‑formula calculations

Today we’ll unlock the secret composition of compounds by turning mass data into formulas. Students should already know atomic masses and basic mole calculations. By the end of the lesson they will be able to derive both empirical and molecular formulas from given experimental data.

1. Do‑now (5') – Quick quiz converting masses to moles.
2. Mini‑lecture (10') – Review mole concept, Avogadro constant and key equations.
3. Guided practice (15') – Walk through the worked example for an empirical formula using the provided table.
4. Pair activity (15') – Students calculate an empirical formula from a new data set.
5. Demonstration (10') – Derive the molecular formula using empirical‑formula mass and a given molar mass.
6. Independent practice (15') – Complete practice questions 1 & 2 while teacher circulates.
7. Check for understanding (5') – Exit ticket: list the steps to obtain a molecular formula.

We reviewed the full pathway from experimental masses to empirical and then molecular formulas, reinforcing the importance of accurate rounding. Students submit an exit ticket summarising the steps, and for homework they will solve an additional set of stoichiometry problems from the textbook.