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 meltingActivity 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 CHeat energy given out Gets hot Hydrochloric acid

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

8 Endothermic ReactionsEndothermic 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 ReactionsEndothermic 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 reactionsStep 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