1. Exothermic and Endothermic Reactions
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2. Endothermic and Exothermic Reactions
Step 1: Energy must be SUPPLIED to break chemical bonds:
Step 2: Energy is RELEASED when new chemical bonds are made:
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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3. Forming Na+ and Cl- ions from NaCl is an endothermic process
a change (e.g. a chemical reaction) that requires (or absorbs) heat.
Forming Na+ and Cl- ions from NaCl is an endothermic process
Photosynthesis is an endothermic reaction (requires energy input from sun.)

4. heat taken in & temperature of the substance drops
Measuring
Heat
reaction
Endothermic Reaction-
heat taken in & temperature of the substance drops

5. Example: Ammonium nitrate + water

6. The starting temperature is 20⁰ C.

7. Add ammonium nitrate to water

8. The temperature decreased by 8⁰C and is now registering at 12⁰C.

9. EXOTHERMIC & ENDOTHERMIC REACTIONS
Exothermic process:
a change (e.g. a chemical reaction) that releases heat.
Burning fossil fuels is an exothermic reaction

10. heat given off & temperature of substance rises.
Heat Released
Measuring
Heat
reaction
Exothermic Reaction-
heat given off & temperature of substance rises.

11. Exothermic vs Endothermic:
more energy is given out than is taken in (e.g. burning, respiration)
ENDOTHERMIC –
energy is taken in but not necessarily given out (e.g. photosynthesis)
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12. Examples Endothermic Photosynthesis Baking bread Evaporation of water
Cooking an egg
Melting ice cubes
Exothermic
Combustion of fuels
Candle flame
Rusting iron
Formation of snow in clouds
Making ice cubes
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