Drill

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Drill 6/7/10

• Give an example of an endothermic reaction and an
  exothermic reaction

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Drill 6/10/11

• Label the parts of the reaction diagram a,b,
  c.
• Is it endo or exo?

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Energy in Chemical Reactions
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What is Energy?

• The ability to do work or produce heat.
• Potential Energy stored energy.
• Kinetic Energy energy of motion.

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What is Enthalpy (?H)?

• The quantity that measures changes in energy in
  systems.
• It has the same of units as energy (kilojoules,
  joules, calories)

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• System the participating members of a reaction
  or change.
• Surroundings everything outside the system.
  This is where we measure energy changes. Whether
  the surroundings gain or lose energy.

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• Endothermic heat energy absorbed
• Exothermic heat energy given off

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What is a Calorimeter?

• An insulated device that measures heat changes in
  a chemical reaction.

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• Heat the total amount of energy transferred.
  Heat transfers from hot to cold. Cold is the
  absence of heat, or energy.
• What is Temperature? average kinetic energy
  (random motion) of all the particles in a system.
  The faster they move, the hotter they are.

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Specific Heat Capacity (c) or (cp)

• Measure how well a substance absorbs or loses
  heat. The amount of heat energy it takes to raise
  the temperature of 1 gram of a substance, 1C.
• UNITS Units in (J/gC) or (cal/gC)
• Low specific heat capacity temperature changes
  easily, ex metals
• High specific heat capacity temp. changes
  slowly, substance retains its heat energy and
  will absorb it slowly. Ex water

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Drill 6/8/11

• 1. What does endothermic mean?
• 2. What does exothermic mean?

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• Chemical Reactions are occurring everywhere.
  From the ignition of your car, to the burning of
  fuel, and the rusting of the gas tank,
  interacting particles will always combine, break
  apart, and reorganize in order to achieve lower
  energy stability

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Reaction Diagram
Products
Potential Energy
Reactants
Reaction
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Activation Energy (Ea) - the minimum energy
necessary to start a chemical reaction. This
energy comes from the surroundings
Ea
Potential Energy
Reaction
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?H is the Change in Enthalpy ?H Energy of
Products Energy of Reactants
Potential Energy
?H
Reaction
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Within the system

• Exothermic Reactions energy is given off from
  the reaction. This will result in a negative
  enthalpy (-?H).

E N E R G Y
Ea
-?H
Reaction
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Within the system

• Endothermic Reactions energy is absorbed from
  the reaction. This will result in a positive
  enthalpy (?H).

E N E R G Y
Ea
?H
Reaction
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What is a catalyst?

• A catalyst is a substance which increases the
  rate of a reaction without being consumed itself.
  
• Effect of a Catalyst a catalyst will lower the
  activation energy of a reaction. This will speed
  up the rate of the reaction.

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Do now!

• Pg. 581 6