Bond Energies

• Is bond breaking endothermic or exothermic?

  Bond breaking is endothermic because energy is required to break bonds
• Is bond forming endothermic or exothermic?

  Bond forming is exothermic because energy is released when new bonds are formed
• What is the formula for calculating the energy change of a reaction using bond energies?

  (energy required to break the bonds of the reactants) - (energy released by forming the bonds of the products)
• Outline the required steps for bond energy calculations

  1. Firstly, find the energy required to break bonds of the reactants
  2. Then, find the energy required to form the new bonds of the products
  3. Then use ‘energy required to break bonds - energy released by forming bonds’ formula to find the overall energy change
• If a chemical reaction has a negative energy change, is it an exothermic or endothermic reaction?

  Exothermic.

  A negative energy change means the products have less energy than the reactants, meaning energy has been released to the surroundings, so the reaction is exothermic.