Question

What does one mean by exothermic and endothermic reactions? Give examples.
NCERT Solutions for Class 10th Science Chapter 1 Chemical Reactions and Equations Exercise 9

NCERT Class X
Science - Science

Chapter_Chemical Reactions and Equations

Answer 1

reaction in which heat energy is liberated by the reactants is called exothermic reaction.
  eg:   Carbon + Oxygen gives  Carbon Dioxide + Q

reaction in which heat energy is absorbed by the reactants is called endothermic reaction.
eg:  Nitrogen + Oxygen gives 2 nitrous oxide (2NO)  -  Q

Answer 2

Answer:-

Exothermic reactions: Those reactions in which energy is released in the form of heat are called exothermic reactions.

Examples –

(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 –