Bond Energies

• What takes place during a chemical reaction?

  Energy must be supplied to break bonds in the reactants

  Energy is released when bonds in the products are formed

  Energy needed to break bonds and energy released when bonds are formed can both be calculated using bond energies
• How do you calculate to overall energy change?

  Sum of energy to break bonds - Sum of energy released when bonds form
• How do you know if a reaction is endothermic?

  When the energy needed to break the bonds is greater than the energy released in forming the products
• How do you know if a reaction is exothermic?

  When the energy needed to break the bonds is less than the energy released in forming the products