Question

Differentiate between the following energy changes in a chemical change with a suitable example :

exothermic and endothermic reaction.

Answer 1

Exothermic reaction- The type of reaction in which heat energy is released to get products from the reaction of reactants is known as an exothermic reaction.

Endothermic reaction- Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products.

Let us understand the differences between the given reaction types-

Endothermic Reaction	Exothermic Reaction
Reactants absorb heat energy from surroundings to form products.	Energy is released in the form of light or heat during the reaction.
These reactions show a cooling effect in the surroundings as the heat has been absorbed.	These reactions cause a rise in the temperature of surroundings.
Energy in the form of heat	Energy is released as heat, electricity, light or sound.
Melting ice, evaporation, cooking, gas molecules, photosynthesis are a few examples	Rusting iron, settling, chemical bonds, explosions, nuclear fission are a few examples.

Endothermic reaction example-

When ammonium chloride (NH₄Cl) is dissolved in water, an endothermic reaction takes place. The salt dissociates into ammonium (NH₄⁺) and chloride (Cl^–) ions.

$\underset{\mathrm{Ammonium}\mathrm{chloride}}{{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}⟶\underset{\mathrm{Ammonium}\mathrm{chloride}}{{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{aq}\right)}–\mathrm{Heat}$

Exothermic reaction example-

The combustion of Methane gives Carbon dioxide and water vapour, and heat energy is released during the reaction.

$\underset{\mathrm{Methane}}{{\mathrm{CH}}_4\left(\mathrm{g}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}\mathrm{vapour}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)}+\mathrm{Heat}$