Chemical Reactions and Equations — Question 9

Exothermic reactions — Reactions in which heat is released along with the formation of products are called exothermic chemical reactions.
For example, burning of natural gas gives out large amount of heat:
CH₄ (g) + 2O₂ (g) ⟶ CO₂ (g) + 2H₂O (g) + Heat

Endothermic reactions — Reactions in which energy is absorbed are known as endothermic reactions.
For example, when carbon is heated with sulphur at high temperature, liquid carbon disulphide is formed:
C + 2S $\xrightarrow{\text{Heat}}$ CS₂