Chemistry · Grade 12

Active learning ideas

Introduction to Hydrocarbons and Isomerism

Welcome to the world of organic chemistry! Begin your journey by exploring hydrocarbons, the simple yet elegant backbone of countless molecules that shape our world.

• Ontario Curriculum Expectations
• Ontario Curriculum: SCH4U, Strand B - Organic Chemistry, B3: Demonstrate an understanding of the structure, properties, and chemical behaviour of compounds within each class of organic compounds.

• 25–45 min
• Pairs → Whole Class
• 3 activities

Activity 01

• Experiential Learning
• 45 min · Pairs

Molecular Model Mania

Using molecular model kits, students build various alkanes, alkenes, and alkynes. They then construct and compare different structural isomers for a given formula, like C5H12, to physically grasp the concept of different atomic arrangements.

Compare the bonding and geometry in alkanes, alkenes, and alkynes.

Facilitation Tip

Encourage students to rotate their models around single bonds to see that it does not create a new isomer.

What to look for

Use an exit ticket where students are given the structure of a branched alkane and must provide the correct IUPAC name, or vice versa.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 02

• Experiential Learning
• 30 min · Whole Class

IUPAC Naming Bee

Organize a classroom competition where students are shown hydrocarbon structures on the board and compete to name them correctly according to IUPAC rules. The activity can be run in rounds with increasing complexity, including branched, cyclic, and unsaturated compounds.

Explain the concept of structural isomerism using examples of simple alkanes.

Facilitation Tip

Have teams write their answers on mini-whiteboards for a quick and engaging way to check for understanding.

What to look for

A quiz or test section that includes a variety of problems: naming complex hydrocarbons, drawing structures from names, identifying functional groups, and drawing all possible structural isomers for a given formula like C6H14.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

Activity 03

• Experiential Learning
• 25 min · Small Groups

Hydrocarbon Card Sort

Prepare cards with hydrocarbon names, structural formulas, and condensed formulas. Students work in small groups to match the corresponding cards, reinforcing the links between names and different types of representations.

Identify the IUPAC names for various branched and cyclic hydrocarbon structures.

Facilitation Tip

Include a few 'trick' cards with incorrect names to challenge students to identify errors in nomenclature.

What to look for

Provide a practice worksheet with a mix of naming and drawing problems. Include a detailed answer key so students can check their work and identify areas where they need more practice.

• Apply
• Analyze
• Evaluate
• Self-Awareness
• Self-Management
• Social Awareness

A few notes on teaching this unit

Begin with physical molecular models to make the 3D structures concrete before moving to 2D representations. Emphasize that IUPAC nomenclature is a logical, rule-based system, much like solving a puzzle. Start with simple straight-chain alkanes and progressively add complexity with branches, multiple bonds, and rings, reinforcing the rules at each step.

Students will learn to identify, draw, and systematically name the core families of hydrocarbons and will be able to recognize and create different structural isomers from a single molecular formula.

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Watch Out for These Misconceptions

• The longest carbon chain is always the one drawn horizontally.

  The longest continuous chain of carbon atoms determines the parent alkane, and this chain can bend and turn. Students must learn to trace all possible paths to find the true longest chain, regardless of how the structure is drawn on paper.

• Different orientations of the same molecule are isomers.

  Structural isomers have different connectivity; atoms are bonded in a different order. Simply rotating a molecule or bending its single bonds creates a different conformation, not a new isomer. Use molecular models to demonstrate the difference between breaking bonds to rearrange (isomer) and simply rotating (conformation).

• When numbering a carbon chain, you can start from either end.

  The carbon chain must be numbered to give the substituents or multiple bonds the lowest possible position numbers. For alkanes, start numbering from the end closest to the first branch. For alkenes/alkynes, the multiple bond takes priority and must be part of the main chain and given the lowest possible number.

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Methods used in this brief

• Experiential Learning