Difference between Endothermic and Exothermic Reactions

This topic explains the difference between Endothermic and Exothermic Reactions. There are a number of chemical reactions in Chemistry and they are divided into many sub and main reactions. Similar is the case with the endothermic and exothermic reactions in Chemistry. These release energy in the form of sound, light, cold or heat.

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In simple terms, the endothermic reactions absorb energy from the surrounding that is in the form of heat. On the other hand, an exothermic reaction releases energy into the surrounding of the system.

A popular example of an endothermic chemical reaction is photosynthesis. During this process, plants absorb energy from the Sun and convert it into carbon dioxide and water into glucose and oxygen. An example of an exothermic reaction is the chemical reaction between sodium and chlorine, producing a bright yellow light and a great amount of heat energy.

Endothermic and Exothermic

Endothermic Reactions

The endothermic process is a term that describes a reaction where the system absorbs the energy from its surrounding in the form of heat. A few examples of the endothermic process are photosynthesis, evaporating liquids, melting ice, dry ice, alkane cracking, thermal decomposition, ammonium chloride in water and much more.

As the name implies, ‘endo’ means ‘to absorb,’ and ‘thermic’ means ‘heat.’

This energy is produced as a result of the reaction of reactants into the product. It occurs as a result of the dissociation of the bonds between the molecules. The energy is then released through the formation of new bonds.

Heat is taken up from the surroundings in such reactions, so the temperature of the system where the reaction is taking place remains cooler. Also, at the end of the reaction, the enthalpy, which is the change in heat energy during the conversion of reactants to products, increases.

Exothermic Reactions

The exothermic reaction is the opposite of an endothermic reaction. It releases energy by light or heat to its surrounding. A few examples are neutralisation, burning a substance, reactions of fuels, deposition of dry ice, respiration, solution of sulphuric acid into water and much more.

The term ‘Exo’ refers to ‘to release,’ and ‘thermic’ refers to ‘heat.’

The energy released is caused by the formation of new bonds (products) at a higher level. While the energy required to break up the bonds (reactants) is lower. At the end of the reaction, the enthalpy change decreases as well. During chemical reactions, a great deal of energy is required. This energy was used to maintain the bond that held the molecules together. As a result of the reactions between molecules and compounds, as well as the breaking of bonds, a tremendous amount of energy is released.

Difference between Endothermic and Exothermic Reactions

Endothermic Reaction

Exothermic Reaction

Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products. An exothermic reaction is a reaction in which energy is released in the form of light or heat.
The energy is absorbed from the surrounding into the reaction. The energy is released from the system to its environment.
Energy in the form of heat. Energy is released as heat, electricity, light or sound.
Melting ice, evaporation, cooking, gas molecules, and photosynthesis are a few examples. Rusting iron, settling, chemical bonds, explosions, and nuclear fission are a few examples.

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Frequently Asked Questions – FAQs


In a chemical reaction, why is heat released or absorbed?

Chemical bonds are either broken or formed in any chemical reaction.
Heat is released when chemical bonds form, and heat is absorbed when chemical bonds break.
Since molecules want to remain together, forming chemical bonds between them requires less energy than breaking them, which requires more energy and results in heat being absorbed from the surroundings.


Define the enthalpy of a reaction.

The enthalpy of a reaction is defined as the heat energy change (HH, H) that occurs when reactants become products. ΔH is positive if heat is absorbed during the reaction; if heat is released, ΔH is negative.


During the endothermic reaction, what type of energy conversion will take place?

This is the conversion of kinetic energy to chemical energy. Heat is absorbed and converted into chemical energy during an endothermic reaction


Why is respiration regarded as an exothermic reaction?

Since energy is released during the process of respiration, it is an exothermic process. The carbon dioxide in the food is broken down to form glucose during the process. This glucose combines with oxygen in our cells, releasing a large amount of energy.


What is the main difference between an exothermic and an endothermic process?

The main difference between exothermic and endothermic reactions is that an endothermic reaction absorbs energy in the form of heat from its surroundings, whereas an exothermic reaction releases energy to the surroundings.

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