This document discusses exothermic and endothermic reactions. Exothermic reactions release energy in the form of heat, causing temperature to rise. Examples given include burning gasoline. Endothermic reactions absorb energy in the form of heat, causing temperature to drop. Examples include cooking pancakes. The key difference is whether more energy is released or absorbed during the reaction.

1. Exothermic and Endothermic
Reactions

2. AGENDA
AIM: To learn about Exothermic and Endothermic reactions
KEYWORDS:
 Exit
 Entry
 High temperature
 Low temperature
EXPLANATION:
 Exothermic reaction with examples
 Endothermic reaction with examples
SUMMARY:
Activity:

3. Energy and Chemical Reactions
• Chemical Energy – Energy stored in the
chemical bonds of a substance.
• Chemical reactions always involve energy
changes.
• Making bonds and breaking bonds
involve energy changes

4. 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

5. Endothermic and Exothermic reactions
Step 1: Energy must be
SUPPLIED to break
chemical bonds of
reactants:
Step 2: Energy is RELEASED
when new chemical bonds are
made in the products:
A reaction is EXOTHERMIC if more energy is RELEASED
than SUPPLIED. If more energy is SUPPLIED than is
RELEASED then the reaction is ENDOTHERMIC
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6. reaction
Endothermic
• Heat (energy) taken in
• Temperature of the substance
drops
• Products feel COLD

7. Endothermic Reactions
• You may see an endothermic reaction written
like this…
REACTANTS + ENERGY PRODUCTS
OR
REACTANTS + HEAT PRODUCTS

8. reaction
Exothermic
• Heat (energy) given off
• Temperature of the substance
rises
• Products feel HOT

9. Exothermic Reactions
• You may see an exothermic reaction written
like this…
REACTANTS PRODUCTS + ENERGY
OR
REACTANTS PRODUCTS + HEAT

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DAILY LIFE EXAMPLES

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DAILY LIFE EXAMPLES

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DAILY LIFE EXAMPLES
Decomposition of vegetable
matter

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Summary:
Exothermic and
Endothermic Reactions

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Activity:
Find out some more examples
of exo & endo reactions

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