Exothermic and Endothermic Reactions

• Exothermic Reaction


  Transfers energy to the surroundings (increases temperature)
• Endothermic Reaction


  Absorbs energy from the surroundings (decreasing temperature)
• Breaking of bonds is an endothermic reaction, as energy is required to break the bonds
• Making bonds is exothermic, as energy is released to form the bond
• Activation Energy

  The minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction
• Bond energy

  Amount of energy needed to break/make a bond
• Energy Change= Energy absorbed - Energy released (J)

  If - is exothermic

  If + is endothermic