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What enthalpy change means

What enthalpy change means

Reaction profile diagrams comparing exothermic and endothermic reactions, with enthalpy axes, activation energy and positive or negative ΔH labelled

Chemical reactions involve breaking bonds and making bonds. Breaking bonds needs energy, making bonds releases energy, and the balance between them gives the enthalpy change, ΔH\Delta HΔH, at constant pressure, usually in kJ mol−1\text{kJ mol}^{-1}kJ mol−1.

Enthalpy changes Lesson

  1. A Level
  2. /Chemistry
  3. /Enthalpy changes

Step-by-step lessons on Edexcel A Level Chemistry Enthalpy changes. Each one builds up to exam-style questions. Build confidence with atomic structure, bonding and moles calculations early on, since these underpin the more demanding organic mechanisms, equilibrium and practical-analysis topics that dominate Year 2.

Lessons