Chemical Reactions and Energy

• Exothermic Reactions


  During these reactions, energy is released to the surroundings
• Endothermic Reactions


  During these reactions, energy is absorbed from the surroundings
• Endothermic reactions are used in hand warmers and ice packs used to cool just-injured areas
• The overall change in energy during a chemical reaction can be calculated by finding the difference between the energy of the products and the energy of the reactants
• Activation energy


  Minimum energy needed to start a reaction
• Exothermic reactions


  Products are at a lower energy level than reactants

  Energy is given out to surroundings
• Endothermic reactions


  Products are at a higher energy level than reactants

  Energy is taken in from surroundings
• Energy change


  Exothermic if negative

  Endothermic if positive