Topic: Chemical Energetics – Exothermic and Endothermic Reactions
Lesson 1: Exothermic and Endothermic Reactions
| Section | Details |
|---|---|
| Objective | (1) State that an exothermic reaction transfers thermal energy to the surroundings, increasing the temperature of the surroundings. (2) State that an endothermic reaction takes in thermal energy, decreasing the temperature of the surroundings. |
| Activities | – Starter (5 mins): Show simple reactions (e.g., combustion of a candle vs. ice melting). Ask: “What happens to the surrounding temperature in each case?” – Main (25 mins): 1. Define exothermic and endothermic reactions with examples. 2. Discuss real-life examples (e.g., hand warmers, cold packs). 3. Conduct a simple experiment (e.g., dissolving NaOH in water for exothermic and NH₄Cl in water for endothermic). – Plenary (10 mins): Students complete a table comparing exothermic and endothermic reactions with examples. |
| Resources | Thermometer, NaOH, NH₄Cl, water, beakers, worksheets for comparison. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write 3 examples each of exothermic and endothermic reactions, explaining their energy changes. |
| Assessment | Worksheet: Identify whether given reactions are exothermic or endothermic and justify. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/20 Q6(a) – Identifying energy transfer in reactions. |
Lesson 2: Enthalpy Change and Activation Energy
| Section | Details |
|---|---|
| Objective | (1) State that the transfer of thermal energy during a reaction is the enthalpy change (ΔH). (2) Define activation energy (Ea) as the minimum energy colliding particles must have to react. |
| Activities | – Starter (5 mins): Show examples of reactions with different energy requirements (e.g., striking a match vs. rusting). Ask: “Why do some reactions start quickly while others are slow?” – Main (25 mins): 1. Explain enthalpy change (ΔH) as negative for exothermic and positive for endothermic reactions. 2. Define activation energy (Ea) and relate it to reaction rates. 3. Show animations or videos of reactions to visualize energy transfer. – Plenary (10 mins): Students draw energy profiles for given reactions, labeling ΔH and Ea. |
| Resources | Diagrams of energy profiles, animations, worksheets with guided examples. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write definitions of ΔH and Ea with diagrams of exothermic and endothermic energy profiles. |
| Assessment | Worksheet: Identify ΔH and Ea in given energy profile diagrams. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/21 Q6(b) – Understanding enthalpy change and activation energy. |
Lesson 3: Reaction Pathway Diagrams
| Section | Details |
|---|---|
| Objective | Draw, label, and interpret reaction pathway diagrams for exothermic and endothermic reactions, including reactants, products, ΔH, and Ea. |
| Activities | – Starter (5 mins): Show incomplete reaction pathway diagrams and ask: “What information is missing?” – Main (25 mins): 1. Teach students how to draw and label reaction pathway diagrams. 2. Provide examples of exothermic (e.g., combustion) and endothermic (e.g., photosynthesis) reactions. 3. Practice interpreting diagrams to describe energy changes. – Plenary (10 mins): Students create labeled diagrams for a provided reaction. |
| Resources | Graph templates, sample diagrams, worksheets for practice. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Draw reaction pathway diagrams for combustion of methane (exothermic) and photosynthesis (endothermic). |
| Assessment | Worksheet: Draw and label reaction pathway diagrams for given reactions. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/19 Q6(c) – Drawing reaction pathway diagrams. |
Lesson 4: Bond Breaking and Bond Making
| Section | Details |
|---|---|
| Objective | State that bond breaking is endothermic and bond making is exothermic. Explain enthalpy change of a reaction in terms of bond breaking and bond making. |
| Activities | – Starter (5 mins): Ask: “What happens when bonds are broken or formed during reactions?” – Main (25 mins): 1. Explain that breaking bonds requires energy (endothermic), while forming bonds releases energy (exothermic). 2. Provide examples and relate to enthalpy changes (ΔH). 3. Discuss how the balance between bond breaking and making determines whether a reaction is exothermic or endothermic. – Plenary (10 mins): Students classify processes (e.g., evaporation, condensation) as bond breaking or making. |
| Resources | Molecular models, diagrams, worksheets for practice problems. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Write explanations for why bond breaking is endothermic and bond making is exothermic. |
| Assessment | Quiz: Classify given reactions as endothermic or exothermic based on bond processes. |
| Past Paper Practice | IGCSE Chemistry 0620/41/O/N/20 Q6(d) – Explaining enthalpy changes via bond breaking/making. |
Lesson 5: Calculating Enthalpy Changes Using Bond Energies
| Section | Details |
|---|---|
| Objective | Calculate the enthalpy change of a reaction using bond energies. |
| Activities | – Starter (5 mins): Show a simple reaction (e.g., H₂ + Cl₂ → 2HCl) and bond energies. Ask: “How can we calculate the energy change?” – Main (25 mins): 1. Explain the formula: ΔH = Σ(bond energies of reactants) − Σ(bond energies of products). 2. Work through examples step by step. 3. Provide practice problems for students to calculate ΔH for various reactions. – Plenary (10 mins): Students solve a summary problem involving ΔH calculation. |
| Resources | Tables of bond energies, worksheets with guided and independent problems, calculators. |
| Time | 40 minutes total: 5 mins (Starter) + 25 mins (Main) + 10 mins (Plenary). |
| Homework | Calculate ΔH for two reactions given bond energies. |
| Assessment | Worksheet: Solve problems calculating enthalpy changes using bond energies. |
| Past Paper Practice | IGCSE Chemistry 0620/41/M/J/21 Q6(e) – Calculating ΔH using bond energies. |
Notes for Teachers:
- Use practical examples and experiments to make energy changes tangible for students.
- Reinforce key concepts (e.g., ΔH, Ea, bond breaking/making) with diagrams and practice problems.
- Emphasize the real-world applications of exothermic and endothermic reactions (e.g., fuels, cold packs).
Leave a Reply