This definitions covers Key Definitions within Bond Energies (HT) for GCSE Chemistry. Revise Bond Energies (HT) in Energy Changes for GCSE Chemistry with 20 exam-style questions and 15 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 8 of 15 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 8 of 15
Practice
20 questions
Recall
15 flashcards
📖 Key Definitions
Bond energy: The energy required to break one mole of a particular type of covalent bond. Units: kJ/mol. The same amount of energy is released when the same bond forms.
ΔH (enthalpy change): The overall energy change in a reaction. Calculated as: ΔH = Σ(energy to break bonds) − Σ(energy released making bonds). Negative = exothermic; positive = endothermic.
Endothermic bond breaking: Breaking any covalent bond always requires energy — it is always endothermic. Work must be done against the electrical attractive force holding the atoms together (like pulling a magnet off a fridge).
Exothermic bond forming: Forming any covalent bond always releases energy — it is always exothermic. When atoms come together, they move into a lower, more stable energy state and release the excess energy to the surroundings.