12. Energy Changes

Definitions
  • Enthalpy change is the net amount of heat given out or taken in during a chemical reaction.
  • Activation energy is the minimum energy possessed by the reactants required to start a reaction.

Exothermic Reaction
  • Energy absorbed in bond breaking is less than energy released in bond forming.
  • Temperature increases.
  • Products have less energy than reactants.
  • Enthalpy change is negative.

Endothermic Reaction
  • Energy absorbed in bond breaking is more than energy released in bond forming.
  • Temperature decreases.
  • Products have more energy than reactants.
  • Enthalpy change is positive.