Exothermic reactions release energy as heat to the surroundings and can occur spontaneously or explosively. Examples include combustion, respiration, and reactions of metals with acids. Endothermic reactions absorb energy from the surroundings and cause cooling. Reversible reactions are exothermic in one direction as they release heat, but are endothermic in the reverse direction as they absorb the same amount of heat.

1. Exothermic and endothermic reactions
What are exothermic and endothermic reactions?
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2. Exothermic and endothermic reactions
What are exothermic and endothermic reactions?
exothermic reactions release energy – they get hot
 ex = out (as in ‘exit’)
 thermic = relating to heat
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3. Exothermic and endothermic reactions
What are exothermic and endothermic reactions?
exothermic reactions release energy – they get hot
 ex = out (as in ‘exit’)
 thermic = relating to heat
endothermic reactions absorb energy – they get cold
 en = in (as in ‘entrance’)
Most chemical reactions are exothermic.
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4. Exothermic reactions
Exothermic reactions release thermal energy (heat)
into their surroundings. Exothermic reactions can
occur spontaneously and some are explosive.
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5. Exothermic reactions
Exothermic reactions release thermal energy (heat)
into their surroundings. Exothermic reactions can
occur spontaneously and some are explosive.
What are some examples?
 combustion
 respiration
 neutralization of acids
with alkalis
 reactions of metals with
acids
 the Thermit Process.
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6. Reversible reactions and energy
Reversible reactions are exothermic in one direction and
endothermic in the other direction. For example:
hydrated anhydrous
copper sulfate copper sulfate
+ water
CuSO4.5H2O CuSO4 + 5H2O
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7. Reversible reactions and energy
Reversible reactions are exothermic in one direction and
endothermic in the other direction. For example:
endothermic
hydrated anhydrous
copper sulfate copper sulfate
+ water
CuSO4.5H2O CuSO4 + 5H2O
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8. Reversible reactions and energy
Reversible reactions are exothermic in one direction and
endothermic in the other direction. For example:
endothermic
hydrated anhydrous
copper sulfate copper sulfate
+ water
CuSO4.5H2O CuSO4 + 5H2O
exothermic
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9. Reversible reactions and energy
Reversible reactions are exothermic in one direction and
endothermic in the other direction. For example:
endothermic
hydrated anhydrous
copper sulfate copper sulfate
+ water
CuSO4.5H2O CuSO4 + 5H2O
exothermic
The amount of energy transferred in each direction is
exactly the same.
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