Q.9: What does one mean by exothermic and endothermic reactions? Give examples.
Exothermic reactions: Those reactions in which energy is released in the form of heat are called exothermic reactions.
(1) All combustion reactions e.g.
CH4 + 2O2 —> CO2 + 2H2O + Heat
(2) Thermite reactions e.g.
2Al + Fe2O3 —> 2Fe + Al2O3 + Heat
Combinations are generally exothermic in nature. The decomposition of organic matters into compost is an example of exothermic reaction.
Endothermic reactions: Those reactions in which energy is absorbed are called endothermic reactions. Examples –
also, the reaction of photosynthesis –