Exo- and Endothermic Reactions

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Exo- and Endothermic Reactions

• Science 9

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Energy Changes in Reactions

• Every chemical reaction either uses energy or
  produces energy in the form of heat

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Exothermic Reactions

• Reactions that produce energy in the form of heat
  or light
• exo means outside and therm means heat
• The energy term written as a product
• 2C2H2 5O2 4CO2 2H2O
  energy

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Exothermic reactions

• Exothermic Reaction a chemical reaction that
  releases energy into its surroundings
• Often, chemical bond energy (when bonds are
  broken) is converted into heat energy
• Reaction warms up its surroundings
• Exothermic reactions can be extremely dangerous!!

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Examples
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Exothermic reaction

• Also includes changes of state
• From Gas?liquid?solid

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Endothermic Reactions

• Reactions that use heat energy
• endo means inside and therm means heat
• The energy term is written as a reactant
• NH4NO3 energy NH4 NO3-

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Endothermic reactions

• Endothermic reaction a chemical reaction that
  absorbs energy from its surroundings
• Chemical endothermic reactions need heat to be
  performed
• Reaction cools down the surroundings (draws in
  heat, so feels cool)

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Endothermic reactions

• Examples
• Cooking food
• Melting of ice
• Photosynthesis
• Changes of state
• From Solid?liquid?gas