bond energies

• What determines whether a reaction is endothermic or exothermic?

  The difference between the energy needed to break existing bonds and the energy released when new bonds are formed
• Why is bond breaking considered an endothermic process?

  Because energy must be absorbed from the surroundings to break the chemical bonds
• What characterizes bond making as an exothermic process?

  Energy is transferred to the surroundings as the new bond is formed
• What indicates that a reaction is endothermic in terms of energy change?

  More energy is absorbed than is released
• What happens to the energy of products in an endothermic reaction?

  The products have more energy than the reactants
• What is the sign of the change in energy for an endothermic reaction?

  Positive
• What is required for bonds to be broken in an endothermic reaction?

  Energy must be absorbed from the surroundings
• What characterizes an exothermic reaction in terms of energy release?

  More energy is released when new bonds are formed than is absorbed to break the bonds
• What happens to the energy of products in an exothermic reaction?

  The products have less energy than the reactants
• What is the sign of the change in energy for an exothermic reaction?

  Negative
• What occurs when new bonds are made in an exothermic reaction?

  Heat is given off to the surroundings
• What are the key differences between endothermic and exothermic reactions?

  • Endothermic reactions:
  • Absorb more energy than released
  • Positive change in energy
  • Products have more energy than reactants
  • Exothermic reactions:
  • Release more energy than absorbed
  • Negative change in energy
  • Products have less energy than reactants