1. Exothermic and Endothermic Reactions
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2. Forming Na+ and Cl- ions from NaCl is an endothermic process
Endothermic Reaction: a process (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)

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

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

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

6. 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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7. Exothermic vs endothermic:
Energy Level
Energy Level
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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8. 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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9. Activation Energy: The energy needed to break chemical bonds to start a chemical reaction.

10. Examples Exothermic Combustion of fuels Yeast & Hydrogen Peroxide
Epson salts & water
Endothermic
Photosynthesis
Acedic Acid & Sodium Bicarbonate
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