5.1.3 · Core · Energetics
Reading the Energy Cliff ⚡
Imagine a marble rolling on a landscape of hills and valleys. That marble is your reaction. Where it ends up tells you everything about energy.
🏔️ The Reaction Landscape
Every chemical reaction has an energy profile — a landscape showing how energy changes from reactants to products. Think of it like Google Maps for chemistry. Two rules:
🔥 Exothermic
Reactants fall OFF the cliff to products. Energy is released to surroundings. Products sit LOWER.
❄️ Endothermic
Reactants are pushed UP the hill. Energy is absorbed from surroundings. Products sit HIGHER.
📌 Reactants start HIGH on the energy axis
📌 Products end LOW — the marble rolled off the cliff
📌 The peak = Activation Energy (Eₐ) — the hill you must climb BEFORE falling
📌 ΔH is negative for exothermic (energy leaves the system)
⚠️ Examiner's Trap #1
Students write "exothermic reactions are hot" — but the diagram shows relative energy of reactants vs products, not temperature. A cold pack (endothermic) still feels cold because it absorbs heat from YOUR HAND, not because the diagram is upside down!
5.1.3 · Energy Profile Diagrams · Core
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