Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Chemistry
Lesson Topic: Describe the formation of poly(ethene) as an example of addition polymerisation using ethene monomers
Learning Objective/s:
  • Describe the step‑wise mechanism (initiation, propagation, termination) of radical addition polymerisation of ethene.
  • Explain the role of a free‑radical initiator and the effect of temperature and pressure on the reaction.
  • Predict how branching influences the density (HDPE vs LDPE) and properties of the resulting polyethylene.
  • Compare addition polymerisation with condensation polymerisation in terms of by‑products and applications.
Materials Needed:
  • Projector or interactive whiteboard
  • Slide set showing the polymerisation mechanism
  • Student handout with reaction equations and key‑features table
  • Sample images of HDPE and LDPE (or physical samples)
  • Whiteboard and markers
  • Exit‑ticket slips for the conclusion
 Introduction:

Begin with a quick question asking students to name a real‑world product made from ethene, then link it to polymer chemistry. Review prior knowledge of covalent bonding and double bonds. State that by the end of the lesson they will be able to describe how ethene monomers link to form polyethylene.
Lesson Structure:
  1. Do‑now (5’) – Write a brief answer to “How does addition polymerisation differ from condensation polymerisation?” and share responses.
  2. Mini‑lecture (10’) – Define addition polymerisation and show the ethene structure; introduce free‑radical initiators.
  3. Mechanism walk‑through (15’) – Use slides to illustrate initiation, propagation, termination; students annotate the handout with the three stages.
  4. Guided practice (10’) – In pairs, complete a flow‑chart that matches each step to its chemical equation and identify the initiator.
  5. Concept check (5’) – Quick Kahoot quiz on reaction conditions and the difference between HDPE and LDPE.
  6. Summary discussion (5’) – Review the key‑features table and connect polymer structure to material properties.
Conclusion:

Recap the three stages of radical addition polymerisation and emphasise that no small molecules are lost. Ask each student to write one exit‑ticket answer describing how temperature influences polymer chain length. For homework, assign a short research task on another addition polymer (e.g., poly(propene)) and its industrial uses.