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Chemical Reactions

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					Chemical Equilibrium and
      Balancing
    Sections 13.2 and 13.3
     Chemical and Physical
          properties
• Chemical properties: things that describe
  the change of one thing to another
  – Wood burns in air, metals rust
• Physical properties: things you don’t have
  to do a reaction to measure
  – Color, density, mp, bp , phase,
         Chemical reaction
• A change that alters the chemical properties
  of a substance - forms a new substance
• Burning something, rusting, decomposition
  are all chemical reactions


      A B C D
     Re ac tan ts           Pr oducts
       Chemical equilibrium
• In every reaction 3
  things take place:
  – Reactants disappear
  – Products form as
    new substances
  – Energy is either
    release or absorbed
    Equations must be equal
• Conservation of mass must apply to chemical
  reactions
• The amount of products and reactants must
  be equal

C  SO2  CS2  CO
5 C  2 SO2  CS2  4 CO
 Types of chemical reactions
• We will study 5 types of chemical
  reactions:
  – Combination reactions
  – Decomposition reactions
  – Endothermic reactions
  – Exothermic reactions
  – Combustion reactions
  – Acid/Base reactions
      Combination reactions
• When at least two reactants combine to form
  just one product
• The product that is formed has completely
  different properties from the reactants

      A B C
      Fe S  FeS
    Decomposition Reaction
• When one reactant breaks down into at least
  two different products
• The products have different properties than
  the reactant

    ABC
    2 MgO  2 Mg  O2
      Endothermic reactions
• Reaction where energy is absorbed from the
  surroundings
• Products will tend to feel colder than
  reactants

       A  energy  B
       A  B  energy  C  D
       3 O2  energy  2 O3
       Exothermic reactions
• Reaction where energy is given off by the
  reaction to the surroundings
• Products will feel warmer than the reactants

A  B  energy
A  B  C  D  energy
CH 4  2 O2  CO2  2 H 2O  energy
      Combustion Reactions
• Reaction where a substance reacts with
  oxygen to burst into flames
• Products will always include CO2 and H2O
• Can include other products also
• Our reactions will only include C, O, and H

 Fuel  O2  Heat  H 2O  CO2
 Cx H y  O2  Ca Ob  CO2  H 2O

				
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posted:11/1/2011
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