1. Endothermic and Exothermic Reactions

2. Exothermic & Endothermic

3. Exothermic Reactions
An exothermic reaction is one which releases heat energy to the surroundings
Temperature increases  Hot

4. Exothermic Reactions Examples include: Burning of fuels. Explosives.
Reaction of acids with metals.
Magnesium reacting with acid
Thermit reaction

5. Charcoal burning A candle burning. A kettle boiling Ice melting
Activity
Say whether these processes are exothermic.
Charcoal burning
A candle burning.
A kettle boiling
Ice melting
A firework exploding
yes
yes no no
yes
You have to put heat in for boiling and melting.
You get heat out from all the other processes

6. Exothermic Reactions Magnesium + Hydrochloric acid 25o C 45o C
Heat
energy
given
out
Gets hot
Hydrochloric
acid

7. Endothermic Reactions
An endothermic reaction is one which takes in heat energy from the surroundings
Temperature decreases  Cold

8. Endothermic Reactions
Endothermic reactions cause a decrease in temperature.
Endothermic chemical reactions are relatively rare.
A few reactions that give off gases are highly endothermic - get very cold.
Dissolving salts in water is another process that is often endothermic.

9. Endothermic Reactions
Endothermic reactions cause a decrease in temperature.
Ammonium
nitrate
Water
Heat
energy
taken
in as the mixture returns back to room temp.
Cools
Starts 25°C
Cools to 5°C
Returns to 25°C

10. Endothermic and exothermic reactions
Step 1: Energy must be SUPPLIED to break bonds:
Step 2: Energy is RELEASED when new bonds are made:
A reaction is EXOTHERMIC if more energy is RELEASED then SUPPLIED. If more energy is SUPPLIED then is RELEASED then the reaction is ENDOTHERMIC