Question

(a) What do you understand by exothermic and endothermic reactions ? 

(b) Give one example of an exothermic reaction and one of an endothermic reaction. 

(c) Which of the following are endothermic reactions and which are exothermic reactions ?

1. Burning of natural gas 

2. Photosynthesis 

3. Electrolysis of water 

4. Respiration 

5. Decomposition of calcium carbonate

Answer 1

(a) Those reactions in which heat is evolved are known as exothermic reactions. The reactions in which heat is absorbed are known as endothermic reactions. 

(b) Example of exothermic reaction:

(c) Endothermic reactions: Photosynthesis, Electrolysis of water, Decomposition of calcium carbonate. 

Exothermic reactions: Burning of natural gas, Respiration.