Exothermic and Exothermic and Endothermic Endothermic

ReactionsReactions

Learning OutcomesLearning Outcomes Describe the term Describe the term exothermicexothermic as a process as a process

or chemical reaction which transfers energy, or chemical reaction which transfers energy, often in the form of heat, to the surroundings often in the form of heat, to the surroundings and may be detected by an increase in and may be detected by an increase in temperature, eg the reaction between temperature, eg the reaction between sodium hydroxide and hydrochloric acid.sodium hydroxide and hydrochloric acid.

Describe the term Describe the term endothermicendothermic as a process as a process or chemical reaction which transfers energy, or chemical reaction which transfers energy, often in the form of heat, from the often in the form of heat, from the surroundings and may be detected by an surroundings and may be detected by an decrease in temperature, eg the dissolving of decrease in temperature, eg the dissolving of ammonium nitrate in water.ammonium nitrate in water.

ExothermicExothermic Process Process or or chemical reactionchemical reaction which which

transfers energy, often in the form of heat, transfers energy, often in the form of heat, toto the surroundings. the surroundings.

May be detected by an May be detected by an increaseincrease in in temperature.temperature.

eg. reaction between eg. reaction between sodium hydroxidesodium hydroxide and and hydrochloric acidhydrochloric acid..

ExamplesExamples

2Mg +O2Mg +O2 2 2MgO 2MgO

Zn + CuSOZn + CuSO44 ZnSO ZnSO44 + Cu + Cu

NN22 + 3H + 3H22 2NH 2NH33

HCHCll + NaOH NaC + NaOH NaCll + H + H22OO

CaCOCaCO33 + 2HC + 2HCll CaC CaCll 22 + + HH22O + COO + CO22

Useful Exothermic Useful Exothermic ReactionsReactions

combustion of fuels

Air bags in cars

self heating cans

Hand warmers

EndothermicEndothermic Process Process or or chemical reactionchemical reaction which transfers which transfers

energy, often in the form of heat, energy, often in the form of heat, fromfrom the the surroundings. surroundings.

May be detected by an May be detected by an decreasedecrease in in temperature.temperature.

eg. the eg. the dissolvingdissolving of of ammonium nitrate in ammonium nitrate in waterwater..

ExamplesExamples

CaCOCaCO33 CaO + CO CaO + CO22

HH22 + I + I22 2HI 2HI

NN22 + O + O22 2NO 2NO

mixing of solids ammonium mixing of solids ammonium thiocyanatethiocyanate and Barium hydroxide and Barium hydroxide

Useful Endothermic Useful Endothermic ReactionsReactions

photosynthesis