Chemestry (How a Chemical Reaction Is Illustrated)

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Lesson #1   Potential Energy Diagrams  

Aim:  How can the process of a chemical reaction be illustrated?

I.    Potential Energy Diagrams = relationship between activation energy and heat of reaction for a chemical reaction 1.    Activated Complex = temporary composite of atoms or molecules that will eventually form the products of the rxn.   = highest point on diagram is potential energy of this composite = energy needed to form this composite = activation energy 2.      Activation Energy - minimum amount of energy needed to form the Activated Complex and start the chemical reaction 3.    Catalyst = atom or molecule that speeds up a chemical reaction when added to the rxn. = lowers peak of Activated Complex b/c takes less energy to make = Heat of reaction and potential energy of products don’t change. 4.     Heat of Reaction = The heat released or absorbed in a chemical reaction.  It is the difference between the Potential Energy of the Products and the Potential Energy of the Reactants

           Heat of Reaction = PE Products - PE Reactants

A.  Exothermic Rxn =     Reactants --> Products + Heat Energy      1.  self-sustaining  i.e. burning match      2.  spontaneous
     3.  Heat of Reaction is negative
     4.  Usually a reaction in which bonds are formed.      5.  Feel warm to the touch as heat is released into the system. [pic]

B.  Endothermic Rxn =     Heat Energy + Reactants --> Products      1.  non-spontaneous
     2.  Heat of Reaction is positive
     3.  Usually a reaction in which bonds are broken.      4.  Feel cold to the touch as heat is removed from the system and absorbed into compounds...
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