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. Energy level diagrams Energy level Activation energy
Using a catalyst might lower the activation energy
Energy given out by reaction
Reaction progress
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4. Forming Na+ and Cl- ions from NaCl is an endothermic process
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)

5. Measuring Heat
reaction
Endothermic reaction, heat taken in & temperature of the substance drops

6. Ammonium nitrate + water

7. Starting temperature 20⁰ C

8. Add ammonium nitrate to water

9. a temperature decrease of 8⁰ C

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

11. Exothermic reaction, heat given off & temperature of substance rises.
Heat Released
reaction
Exothermic reaction, heat given off & temperature of substance rises.

12. Exothermic vs endothermic:
EXOTHERMIC – 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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13. Examples Exothermic Combustion of fuels Yeast & Hydrogen Peroxide
Epson salts & water
Endothermic
Photosynthesis
Acedic Acid & Sodium Bicarbonate
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