Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Chemistry
Lesson Topic: Describe the properties of alkanes as being generally unreactive, except in terms of combustion and substitution by chlorine
Learning Objective/s:
  • Describe the general physical properties of alkanes and explain trends with chain length.
  • Explain why alkanes are largely unreactive, referencing bond energies and lack of polarity.
  • Outline the combustion reaction of alkanes and predict its products.
  • Describe the free‑radical chlorination mechanism with chlorine, identifying initiation, propagation, and termination steps.
  • Compare the reactivity of alkanes with that of alkenes and alkynes.
Materials Needed:
  • Projector and screen for slides/diagrams
  • Whiteboard and markers
  • Printed worksheet with reaction equations and mechanism diagram
  • Molecular model kit (alkane models)
  • Safety goggles and a UV lamp for the halogenation demo
  • Calculator for stoichiometry calculations
 Introduction:
Begin with a quick demonstration of a blue‑white flame from a Bunsen burner to capture interest. Review prior knowledge of hydrocarbons and the formula CnH2n+2. State that by the end of the lesson students will be able to describe why alkanes are mostly inert and predict the two main reactions they do undergo.
Lesson Structure:
  1. Do‑now (5') – short quiz on hydrocarbon families and write the alkane formula; teacher checks answers.
  2. Mini‑lecture (10') – present physical properties and trends using slides and model kits.
  3. Concept discussion (8') – explore bond energies and polarity; think‑pair‑share on why alkanes are unreactive.
  4. Demonstration (12') – combust a small amount of propane; discuss products and energy release.
  5. Guided practice (15') – worksheet activity on the free‑radical chlorination mechanism; fill in initiation, propagation, termination steps while teacher circulates.
  6. Quick check (5') – exit‑ticket: write one example of an alkane reaction with its balanced equation.
Conclusion:
Summarise that alkanes are largely inert except for combustion and UV‑induced halogenation, highlighting the key steps of the radical mechanism. Collect exit‑tickets and remind students to complete the homework worksheet comparing alkane reactivity with alkenes. Homework: finish the worksheet and bring examples of real‑world uses of alkanes.