CBSE Class 10 Answered

Exothermic Reaction

The chemical reactions which proceed with the evolution of heat energy are called exothermic reactions.

Examples:

Carbon burns in oxygen to form carbon dioxide and heat energy is produced.

 C  +  O₂  →  CO₂  +  Heat

Water added to quick lime (calcium oxide), slaked lime (calcium hydroxide) is produced with a lot of heat energy.

CaO  +  H₂O  →  Ca(OH)₂  +  Heat

Endothermic Reaction

The chemical reactions which proceed with the absorption of heat energy are called endothermic reactions.

Examples:

When nitrogen and oxygen are heated together to a particular temperature of about 3000^oC, a nitric oxide gas is formed.

N₂  +  O₂  +  Heat  →   2NO

Calcium carbonate decomposes into carbon dioxide and calcium oxide when heated to a temperature of about 1000oC.

CaCO₃  +  Heat  →  CaO  +  CO₂

 Now, you know what is endothermic reactions and exothermic reactions,

if you observed carefully, in exothermic reactions heat is evolved and in endothermic heat is required, in this way you can easily find out the type of reaction.