What does one mean by exothermic and endothermic reactions ? Give examples.

Explanation

Exothermic reactions: The reactions in which heat is given out along with the products are called.exothermic reactions.
Examples :
(i) When quick lime reacts with water, slaked lime is produced with evolution of heat.
`underset("Quick lime")(CaO(s)) + H_2O(l) rarr underset("Slaked lime")(Ca(OH)_2(aq))" + Heat"`
(ii) Burning of natural gas.
`CH_4(g) + 2O_2 (g) rarr CO_2(g) + 2H_2O(l)" + Heat"`
Endothermic reactions. The reactions in which energy is absorbed are known as endothermic reactions.
Examples :
(i) `underset("sulphate")underset("Ferrous")(2FeSO_4(s)) overset("Heat")to underset("oxide")underset("Ferric")(Fe_2O_3(s)) + underset("dioxide")underset("Sulphur")(SO_2(g)) + underset("trioxide")underset("Sulphur")(SO_3(g))`
(ii) `underset("Lead nitrate")(2Pb (NO_3)_2 (s)) overset("Heat")to underset("oxide")underset("Lead")(2PbO(s)) + underset("dioxide")underset("Nitrogen")(4NO_2(g)) + underset("Oxygen")(O_2(g))`