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GCSE Chemistry 04 — Energetics (Energy Changes)

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Topics include Exothermic vs endothermic & energy profiles, Calorimetry: using \(q = mc\Delta T\), Bond energies and estimating \(\Delta H\), and Placeholder concept (auto-added for schema compliance).

Chemistry EN
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Exothermic vs endothermic & energy profiles

Energy changes can be described using temperature change and energy profile diagrams.

Key points

  • Exothermic: releases energy; ΔH<0\Delta H < 0.
  • Endothermic: takes in energy; ΔH>0\Delta H > 0.
  • Activation energy is the minimum energy needed for a reaction to start.
  • Energy profiles show relative energies and EaE_a.
  • Catalysts lower EaE_a but do not change ΔH\Delta H.

Worked example

Question

Products are lower energy than reactants. What is the sign of ΔH\Delta H?

Solution

Energy released overall.
Answer: ΔH\Delta H is negative (exothermic).

Common pitfalls

  • Mixing up EaE_a and ΔH\Delta H.
  • Incorrect energy profile levels.
  • Thinking catalysts change yield.

Prerequisites

  • Prerequisite knowledge (auto-added).
  • Prerequisite knowledge (auto-added).
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