Topic: Stoichiometry – 3.1 Formulae
Lesson 1: Formulae of Elements and Compounds
| Section | Details |
|---|---|
| Objective | State the formulae of the elements and compounds named in the subject content. |
| Activities | – Starter (5 mins): Show the periodic table and discuss how symbols represent elements (e.g., H₂, O₂). – Main (25 mins): 1. Explain the rules for writing chemical formulae for elements and compounds (e.g., NaCl, CO₂, H₂O). 2. Provide examples of common compounds and their formulae. – Plenary (10 mins): Students match chemical names to their correct formulae (e.g., ammonia → NH₃). |
| Resources | Periodic table, worksheets with element and compound names, flashcards. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write the chemical formulae for a list of compounds provided (e.g., sulfuric acid, methane). |
| Assessment | Worksheet: Identify elements and compounds by their formulae. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q1(a) – Writing chemical formulae for elements and compounds. |
Lesson 2: Molecular and Empirical Formulae
| Section | Details |
|---|---|
| Objective | Define molecular formula as the number and type of atoms in one molecule. Define empirical formula as the simplest whole number ratio of the different atoms or ions in a compound. |
| Activities | – Starter (5 mins): Show molecular diagrams (e.g., glucose, CH₄). Ask students: “What do these diagrams tell us about the molecule?” – Main (25 mins): 1. Define molecular formula with examples (e.g., H₂O, C₂H₆). 2. Define empirical formula and compare it with molecular formula using examples (e.g., C₂H₆ → CH₃). 3. Practice deducing empirical formulae from molecular formulae. – Plenary (10 mins): Group activity: Determine molecular and empirical formulae for compounds given their atomic ratios. |
| Resources | Molecular model kits, diagrams, worksheets for practice. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Calculate the empirical formula of compounds given molecular formulae (e.g., H₂O₂, C₄H₁₀). |
| Assessment | Worksheet: Define and calculate molecular and empirical formulae. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q2(b) – Calculating empirical formulae. |
Lesson 3: Deduction of Formulae
| Section | Details |
|---|---|
| Objective | Deduce the formula of simple compounds from the relative numbers of atoms or ions in a model or diagrammatic representation. Deduce the formula of an ionic compound from the charges on the ions. |
| Activities | – Starter (5 mins): Show ionic compound diagrams and ask students to predict the formula. – Main (25 mins): 1. Explain how to deduce formulae from models (e.g., CO₂, H₂O). 2. Teach students to use ion charges to deduce the formula of ionic compounds (e.g., Na⁺ and Cl⁻ → NaCl, Ca²⁺ and O²⁻ → CaO). 3. Practice deducing formulae for given ions. – Plenary (10 mins): Students solve questions to deduce formulae of simple compounds and ionic compounds. |
| Resources | Diagrams of compounds, worksheets with ions and atomic models, periodic table. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Deduce the formulae of ionic compounds (e.g., Mg²⁺ and Cl⁻, Al³⁺ and O²⁻). |
| Assessment | Worksheet: Deduce formulae from diagrams and ionic charges. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q3(a) – Deduction of ionic compound formulae from charges. |
Lesson 4: Chemical Equations
| Section | Details |
|---|---|
| Objective | Construct word equations, symbol equations, and ionic equations to show how reactants form products, including state symbols. |
| Activities | – Starter (5 mins): Write a simple word equation (e.g., hydrogen + oxygen → water). Ask students to identify the reactants and products. – Main (25 mins): 1. Teach the steps for writing word, symbol, and ionic equations. 2. Practice converting word equations into balanced chemical equations with state symbols. 3. Discuss the importance of including state symbols (e.g., (s), (l), (g), (aq)). – Plenary (10 mins): Students construct balanced equations for given reactions (e.g., combustion of methane, neutralization of HCl with NaOH). |
| Resources | Reaction cards, worksheets with unbalanced equations, periodic table. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write balanced symbol equations with state symbols for five given reactions. |
| Assessment | Worksheet: Convert word equations to balanced symbol equations, including state symbols. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q3(b) – Writing balanced equations with state symbols. |
Notes for Teachers:
- Use visual aids like molecular models and diagrams to help students visualize formulae.
- Reinforce the importance of balancing equations and including state symbols.
- Provide plenty of practice questions for empirical formula calculations and chemical equations.
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