UNIT OVERVIEW

This revision unit brings together all the key topics from Term 2. You will consolidate your understanding of light behaviour, gas laws, stoichiometry, and energy changes in reactions. The focus is on exam preparation—understanding concepts, applying formulas correctly, and avoiding common mistakes.

What you will revise:

• Refraction, critical angles, and total internal reflection
• Wavefronts, diffraction, and Huygens' principle
• Gas laws and ideal gas calculations
• Stoichiometry including limiting reagents and percentage yield
• Energy changes in chemical reactions and enthalpy diagrams

Why these topics matter:

• Fibre optic cables use total internal reflection to carry internet data across South Africa.
• Weather balloons expand as they rise because pressure decreases with altitude—this is the gas laws in action.
• Medicine manufacturing relies on stoichiometry to calculate exact quantities of reactants.
• Instant cold packs used in sports medicine contain chemicals that absorb heat (endothermic reactions).

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