Exothermic and Endothermic Changes Part 1

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Chapter 3

• Exothermic and Endothermic Changes Part 1

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• All changes whether physical or chemical involve
  a change in energy.
• Energy can be released during the change
  (exothermic).
• Energy may be absorbed during the change
  (endothermic).
• The amount of energy that is released or absorbed
  in measured in joules or calories.

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Energy Change and Bond Breakage/Formation
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Energy Change and Bond Breakage/Formation

• Bonds are energy.
• Each different type of bond has an amount of
  energy associated with it.

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Energy Change and Bond Breakage/Formation

• Bonds are energy.
• Each different type of bond has an amount of
  energy associated with it.
• When we break a bond the process requires energy
  (it is endothermic).
• When we form a bond the process releases energy
  (it is exothermic).
• The net energy change determines whether the
  reaction is endothermic or exothermic.

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Energy Change and Bond Breakage/Formation

• 2H-H O - O ? 2

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Energy Change and Bond Breakage/Formation

• We can often determine whether energy is being
  released or absorbed by a reaction by determining
  if any temperature change occurs.

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Temperature Change

• Exothermic reactions often feel hot.

• Endothermic reactions often feel cold.

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Exothermic/Endothermic Demos
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Homework

• Worksheet 3-1 (due tomorrow)