Lesson Plan

• Describe why cracking of large alkanes is performed in the petrochemical industry.
• Explain how temperature, pressure, catalyst acidity and residence time influence cracking outcomes.
• Compare thermal, steam and catalytic cracking methods and their typical product ranges.
• Interpret a simple cracking reaction equation and identify the resulting alkane and alkene fragments.
• Evaluate the economic and environmental benefits of cracking for fuel and chemical production.

• Projector and screen
• Whiteboard and markers
• Printed worksheet with cracking equations
• Molecular model kits (alkane & alkene)
• Short video of a refinery cracking unit
• Handout summarising key factors and types of cracking
• Exit‑ticket cards

Begin with a quick question: “What happens to a heavy oil barrel when it’s heated?” Connect this to students’ prior knowledge of hydrocarbon families and ask them to predict the products. Explain that today’s success criteria are to identify why cracking is essential and to describe the main factors that control it.

1. Do‑now (5') – Students list examples of alkanes and alkenes on a sticky note.
2. Mini‑lecture (10') – Define cracking, present the industrial reasons (value, fuel quality, market demand, handling, economics, impurity removal).
3. Interactive diagram (10') – Using the projector, label the five key factors (temperature, pressure, catalyst acidity, residence time, molecular size) and discuss their effects.
4. Video demonstration (5') – Show a short refinery cracking clip; pause to highlight temperature and catalyst differences.
5. Group activity (15') – In small groups, balance a thermal cracking equation (e.g., C₁₂H₂₆ → C₈H₁₈ + C₄H₈) and classify each product as alkane or alkene.
6. Compare methods (10') – Fill‑in a table contrasting thermal, steam, and catalytic cracking (conditions, catalysts, main products).
7. Formative check (5') – Exit‑ticket: “State one reason why industry cracks large alkanes and one factor that influences the product distribution.”

Recap the five influencing factors and the three cracking types, emphasizing how each reason supports industry goals. Collect exit‑tickets to gauge understanding, then assign a brief homework: research one real‑world product derived from a cracking‑generated alkene and write two sentences on its importance.