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

Explanation

Exothermic reaction: Reactions in which energy is released in the form of heat, light, or sound along with the formation of products are called exothermic reactions.
Examples :
Mixture of sodium and chlorine to yield table salt :
`2Na +Cl_(2) to 2NaCl +411kJ` of energy
Burning of natural gas :
`CH_(4)(g) +2O_(2)(g) to CO_(2)(g) +2H_(2)O(g)`
We get energy to stay alive from the food we eat. During digestion, food is broken down into simpler substances. For example, rice, potatoes and bread contain carbohydrates. These carbohydrates are broken down to form glucose. This glucose combines with oxygen in the cells of our body and provides energy. The special name of this reaction is respiration.
`underset("(Glucose)")(C_(6)H_(12)O_(6)(aq)) +6O_(2)(aq) to 6CO_(2)(aq) +6H_(2)O(l) +` Energy
The decomposition of vegetable matter into compost is also an example of an exothermic reaction.
Endothermic reaction : Reactions in which energy is absorbed or required energy either in the form of heat, light or electricity for breaking down the reactants are known as endothermic reactions.
Example :
In the process of photosynthesis, plants use the energy from the sun to convert carbon dioxide and water to glucose and oxygen.
`6CO_(2)+6H_(2)O(l) overset("Sunlight")to underset("(Glucose)")(C_(6)H_(12)O_(6)(aq)) +6O_(2)(g)`
Endothermic reactions:
`CaCO_(3)(s) overset(Delta)toCaO(s) +CO_(2)(g)`
`N_(2)(g) + O_(2)(g) overset("Electric discharge")to2NO(g)`