Difference Between Exothermic and Endothermic (With Table)

Chemical reactions occur daily in our surroundings. However, we often never notice them. The process of a chemical reaction involves two substances reacting to each other and forming a completely new substance. These can be categorized under exothermic and endothermic reactions. Each of them has its own parameters and characteristics.

Exothermic vs Endothermic

The difference between exothermic and endothermic is that an exothermic reaction is that which gives out energy into the surrounding environment in the form of light, sound, electricity, etc. when it takes place whereas an endothermic reaction is that which absorbs energy from the surrounding environment in the form of heat when it takes place.

The characteristic that sets an exothermic reaction apart is that energy is released during the process. Sometimes, this energy is even greater in amount than what was required to carry out the reaction in the first place. An example of an exothermic reaction is when a gas condenses into liquid. Here, heat is released into the environment.

Meanwhile, the main characteristic of an endothermic reaction is that it absorbs energy from the surroundings during the process. This energy is only in the form of heat. An example of such a reaction is the boiling of water. When such a process is carried out, the water absorbs heat, making it an endothermic reaction.

Comparison Table Between Exothermic and Endothermic

Parameters of ComparisonExothermicEndothermic
MeaningIt is a chemical reaction that involves the release of energy into the surrounding environment.It is a chemical reaction that involves the absorption of energy from the surrounding environment.
Energy FormThe released energy may be in the form of heat, sound, light, electricity, etc.The absorbed energy is always in the form of heat.
TemperatureWhen the process is carried out, the temperature gradually decreases.When the process is carried out, the temperature gradually increases.
EnthalpyIn relation to the products of the reactants, the enthalpy is always lower.In relation to the products of the reactants, the enthalpy is always higher.
Change in EnthalpyWhen the change in enthalpy is calculated, it is always a positive value.When the change in enthalpy is calculated, it is always a negative value.
ExampleAn example of an exothermic reaction is the condensing of gas to liquid.An example of an endothermic reaction is boiling water.

What is Exothermic?

When heat and other forms of energy are given out to the surroundings during a chemical reaction, it is termed an exothermic reaction. The enthalpy is always of a lower value than the product of the reactants. Moreover, when the change in enthalpy is calculated, it is always a positive value for such reactions. A good way to characterize exothermic reactions is to monitor the temperature as it decreases.

For bonds to be continuously formed and broken during the process, a certain amount of energy is needed. In exothermic reactions, the energy being produced during the process is greater than that required to break the bonds. As a result, excess energy is given out into the environment as it no longer helps the reaction.

A great example of an exothermic reaction is a campfire. Almost everyone has experienced the heat while sitting around it. In this case, a reaction between oxygen and cellulose takes place when the wood is burnt. As a result, warmth is released into the surroundings.

This kind of reaction also takes place when a rocket launches. During this process, one can notice the large cloud of steam and smoke being dispersed from the lower end of the vehicle. This is due to the exothermic reaction that occurs during the consumption of fuel.

What is Endothermic?

When heat is absorbed during the process of a chemical reaction, it is termed an endothermic reaction. This is the only form of energy involved in the process. The reaction is a contrast to exothermic reactions as it is characterized by a lower enthalpy value than that of the product of the reactants. Moreover, when the change in enthalpy is calculated, it is always a negative value for such reactions.

During the process, bonds are continuously formed and broken. In such reactions, a greater amount of energy is needed to break the bonds than the amount of energy being generated by the reaction. Therefore, a certain amount of energy is absorbed to do so. Moreover, the temperature gradually increases as this happens.

A great example of an endothermic reaction is the boiling of water. A certain temperature point needs to be reached for water to be boiling. This is achieved by absorbing heat from the surroundings. In this particular case, it is from the fire used for boiling.

Other examples of an endothermic reaction include evaporation, thermal decomposition, hydrolysis, cracking of alkanes, sublimation, nuclear fission and even dissolving certain chemicals such as citric acid and baking soda. Each of these absorbs a certain amount of energy for taking place.

Main Differences Between Exothermic and Endothermic

  1. Exothermic reaction involves the release of energy into the surrounding environment whereas endothermic reaction involves absorption of energy from the surrounding environment.
  2. Exothermic reaction releases energy as heat, sound, light, electricity, etc. whereas endothermic reaction absorbs energy only as heat.
  3. When an exothermic reaction is carried out, the temperature gradually decreases whereas when an endothermic reaction is carried out, the temperature gradually increases.
  4. In relation to the products of the reactants, the enthalpy is always lower for exothermic reactions whereas, for the latter, the enthalpy is always higher.
  5. When the change in enthalpy is calculated, it is always a positive value for exothermic reactions whereas, for endothermic reactions, it always has a negative value.
  6. An example of an exothermic reaction is the condensing of gas to liquid whereas that of endothermic reactions is boiling water.

Conclusion

Exothermic and endothermic are two different kinds of reactions that have different effects when they take place. Firstly, an exothermic reaction gives off energy while an endothermic reaction absorbs it. This is due to the amount of energy required to break the chemical bonds when the process takes place. If the energy produced is higher, an exothermic reaction takes place whereas if the energy produced is lower, an endothermic reaction takes place.

Another major difference between the two is that an exothermic reaction gives out energy in various forms whereas an endothermic reaction only absorbs energy in one form, that is heat.

References

  1. https://aiche.onlinelibrary.wiley.com/doi/abs/10.1002/aic.690421018
  2. https://www.cambridge.org/core/journals/journal-of-fluid-mechanics/article/endothermic-and-exothermic-chemically-reacting-plumes/F0C1BD48CB20CD66782D330FF738035A
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