L4 Structural Isomerism (Unit 5 Chemistry BTEC Applied Science)

This PowerPoint lesson covers Structural Isomerism for Pearson BTEC Applied Science Unit 5 Chemistry, including chain, position and functional-group isomerism. It is designed to help students understand why compounds can share the same molecular formula while having different structural formulae and chemical identities.

Structural isomerism occurs when two or more compounds have the same molecular formula but different connectivity of atoms. The lesson begins by distinguishing molecular formulae from structural formulae and then introduces the idea of isomers and structural isomers. Students also briefly compare structural isomerism with stereoisomerism in preparation for later work on E/Z and cis/trans isomerism.

The resource develops the three main types of structural isomerism. Chain isomerism is explored using straight-chain and branched compounds such as butane and 2-methylpropane. Position isomerism is illustrated using halogenoalkanes, alcohols and alkenes, including 1-chloropropane and 2-chloropropane, butan-1-ol and butan-2-ol, and but-1-ene and but-2-ene. Functional-group isomerism is introduced using propanal and propanone, alongside cyclic and open-chain examples such as cyclohexane and hexene.

Students are also taught a systematic method for drawing and naming all possible structural isomers of a molecular formula, including a worked example using C₄H₉Cl. The fully editable PowerPoint (.pptx) includes learning objectives, key terminology, retrieval starters, worked examples, drawing activities, answer slides and end-of-lesson check-your-understanding questions. Updated in October 2026, it is suitable for classroom teaching, revision, cover work or independent study within Pearson BTEC Applied Science Unit 5 Chemistry.