What is Difference between Endothermic and Exothermic Reactions?

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Difference between Endothermic and Exothermic Reactions: When an element or a compound reacts with another to generate a new product, this is referred to as a chemical reaction. It alters the atomic configuration. The major difference between endothermic and exothermic reactions is that in endothermic enthalpy increases whereas in exothermic enthalpy is negative. It either absorbs or releases energy to bring about the changes and for the reaction to occur. A chemical reaction is classified into two types based on this:

  • Exothermic Reactions
  • Endothermic Reactions

Endothermic reactions absorb energy in the form of heat from their surroundings. An exothermic reaction, on the other hand, discharges energy into the system’s surroundings. Here, we have discussed the difference between endothermic and exothermic reactions along with the introduction to endothermic and exothermic reactions in the upcoming sections.

Difference Between Endothermic and Exothermic Reactions

We have provided the difference between endothermic and exothermic reactions listed in the table below. 

Key Differences Between Endothermic and Exothermic Reactions

Endothermic Reaction Exothermic Reaction
Endothermic reactions are chemical reactions that produce products by absorbing heat energy from their environment. An exothermic reaction is one that releases energy in the form of light or heat.
Enthalpy increases as heat are absorbed. As heat is evolved, enthalpy is negative.
The reaction absorbs energy from its surroundings. The system’s energy is released into the environment.
The process involves the use of heat energy.  Heat is produced as a byproduct of the process.
Heat is emitted as a form of energy. Heat, electricity, light, and sound are all forms of energy.

What is Endothermic Reaction?

As the name implies, endo means ‘to absorb,’ and thermo means ‘heat’. The endothermic process is a reaction in which the system absorbs energy from its surroundings in the form of heat. Endothermic processes include photosynthesis, evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, ammonium chloride in water, and many others. This energy is created by the reaction of reactants into the product. It happens as a result of the dissociation of the molecules’ bonds. The energy is then released as new bonds are formed.

Thus, endothermic reactions can be defined as chemical reactions in which energy is absorbed. This energy is generated by the reaction of reactants into products. It is caused by the breakdown of the bonds between molecules. The energy is then released through the production of new bonds. Heat is drawn up from the surroundings in such reactions, therefore the temperature of the system where the reaction is taking place remains colder. Also, at the end of the reaction, the enthalpy, which is the change in heat energy during the conversion of reactants to products, increases.

What is Exothermic Reaction?

The terms ‘Exo’ refers to ‘release’ and ‘thermic’ refers to the ‘heat’. As a result, exothermic processes involve the release of energy. These types of reactions are hotter, and they can be harmful in high-rate reactions.

The energy released is caused by the production of new bonds (products) at a higher level. While the energy required to break up the bonds (reactants) is smaller. At the completion of the process, the enthalpy change decreases as well. During chemical processes, a significant amount of energy is required. This energy was required to maintain the link that held the molecules together. So there is a great quantity of energy released with the reactions between molecules and compounds, with the breaking of bonds.

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