Energy Change & Rates of Reactions

• Heat of reaction

  the net change of chemical potential

  energy of the system
• Exothermic Reactions

  reactions which transform chemical

  potential energy into thermal energy
• Endothermic reactions

  reactions which transform thermal

  energy into chemical potential energy
• Activation energy

  the minimum energy required to start a chemical reaction
• Activated complex

  a high energy, unstable transition

  state between the reactants and the products
• reaction rate

  the change in amount or concentration per unit time of either a reactant or product
• Catalyst

  a substance that increases the rate of

  the reaction but remains unchanged at the end of the

  reaction