Chemical Reactions

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Chemical Reactions

• Ch.21 Sec.1

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Chemical Reactions

• Occurs with chemical changes
• Make new substances
• Change in which one or more substances are
  converted into new substances

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Signs of Chemical Reactions

• Change in color
• Release of light, heat, gas, sound, or smell

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Examples of Chemical Reactions

• Growing
• Ripening
• Decaying
• Burning
• Rusting

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Law of Conservation of Mass

• Mass cannot be created or destroyed
• Chemical reactions rearrange atoms
• Break bonds, rearrange, and make new bonds
• Energy breaks bonds

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Chemical Equation

• A way to describe a chemical reaction using
  chemical formulas and other symbols
• Pg. 635 Table 1 and equation

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Products Reactants

• Reactants left side of equation (ALWAYS)
• Products right side of equation (ALWAYS)

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Chemical Equations

• Balanced chemical equation has same number of
  atoms of each element on both sides of the
  equation
• Satisfies the Law of Conservation of mass.

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Reaction Types

1. Synthesis
2. Decomposition
3. Single Displacement
4. Double Displacement
5. Combustion

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Synthesis

• Combines 2 substances to make 1 compound
• A B --gt AB
• Blue Red --gt Purple
• Na Cl --gt NaCl
• 1 Product

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Synthesis
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Decomposition

• Takes 1 compound and breaks it apart into 2 or
  more substances
• AB --gt A B
• H2O --gt H2 O2
• Opposite of synthesis
• 1 Reactant

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Decomposition
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Single-Displacement

• 1 element swaps places with another element that
  is in a compound
• XA B --gt XB A
• B and A swapped places
• Has 1 compound and 1 element on both sides
• Ex CuCl2 Al --gt AlCl3 Cu

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Single-Displacement
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Double - Displacement

• 2 compounds exchange elements with each other
• AX BY --gt AY BX
• 2 Compounds on both sides
• Ex NaCl AgF ? NaF AgCl

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Double - Displacement
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Combustion

• Oxygen and another compound BURN to make new
  products
• Oxygen is ALWAYS a reactant
• CO2 H2O is ALWAYS a product
• Ex CH4 O2 --gt CO2 H2O

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What Type of Reaction?

• Double Displacement
• Decomposition
• Single Displacement
• Synthesis

1. HCl NaOH --gt H2O NaCl
2. NaCl --gt Na Cl2
3. Al Fe2O3 --gt Al2O3 Fe
4. P4 O2 --gt P4O10

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2 Types Energy Reactions

• Endothermic
• Exothermic

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Endothermic

• Endo in
• Energy is taken in (absorbed) with reactants
• Drops surrounding environment temp.
• Ex Photosynthesis - takes in sunlight

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Exothermic

• Exo out
• Energy is released or given out with products
• Raises surrounding environments temperature
• Ex hand warmers

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Exo or Endo?

• Exo
• Exo
• Endo
• Exo

1. Paper burning
2. Firecracker Exploding
3. Plant making its own food
4. Electric blanket

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Reaction Rate

• How fast a reaction is going
• Factors on rate
• Temperature
• Surface Area
• Concentration
• Stirring
• Catalysts

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Catalysts

• Substance that speeds up reaction without being
  permanently changed
• Ex Enzymes in our stomach speed up digestion
  (lactose)

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Inhibitors

• Substance used to slow down a chemical reaction
• Ex Food preservatives (prevent spoilage)
• Product is not changed just how fast or slow the
  rate of production occurs