Chemistry of Matter 24 Energy of Chemical Reactions

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Chemistry of Matter 2-4Energy of Chemical
Reactions
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Energy of Chemical Reactions

• Based on the type of energy (heat) change
  involved, chemical reactions are classified as
  either exothermic or endothermic.
• Exothermic energy is released
• Exo- exit
• Burning of gasoline
• Endothermic energy is absorbed
• Endo- into
• Cooking of pancakes

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Exothermic
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Endothermic
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ENERGY (continued)

• Chemical reactions require energy.
• The energy required for a chemical reaction to
  occur is called activation energy.

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Activation Energy
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Chemistry of Matter 2-5Rates of Chemical
Reactions
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Rates of Chemical Reactions

• Kinetics is the study of reaction rates.
• The rate of reaction is a measure of how quickly
  reactants turn into products.
• The Collision Theory relates particle collisions
  to reaction rate.
• The rate of reaction is affected by FOUR factors
  concentration, surface area, temperature, and
  catalysts.
• The greater the number of collisions, the higher
  the reaction rate.

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Concentration
Concentration is the measure of the amount of
substance in a given unit of volume. Most
reactions proceed at a faster rate if the
concentration of reactants is increased.
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Surface Area
The rate of reaction can be increased by breaking
the solid into smaller pieces.
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Temperature
An increase in temperature generally increases
the rate of reaction.
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Catalysts
A catalyst is a substance that usually increases
the rate of reaction but is not itself changed by
the reaction.
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Changes harmful gases into harmless gases.