Endothermic and Exothermic Reactions (original) (raw)

Last Updated : 23 Jul, 2025

Endothermic and exothermic reactions are the two primary types of chemical reactions based on the energy changes that take place throughout the reaction. Understanding the distinctions between these terms—which characterize whether a reaction consumes or releases energy is essential for comprehending the behavior of chemical systems. Let's examine more closely how endothermic and exothermic processes differ from one another.

What is an Endothermic Reaction?

The phrase "endothermic process" refers to a chemical reaction in which the system takes in heat energy from its environment. Examples of this include liquids evaporating, ice melting, dry ice melting, alkanes breaking, thermal breakdown, etc.

The words "**endo" and "**thermic," as their names imply, mean "to **absorb" and "**heat," respectively.

As a result, endothermic reactions can be described as chemical processes in which energy is absorbed. The transformation of reactants into the product is what generates this energy. The dissolution of the molecules' bonds is the cause of this. The energy is then released when new bonds are formed. Such reactions absorb heat from the environment, keeping the system where the reaction is taking place colder as a result. Additionally, when reactants are transformed into products towards the conclusion of the reaction, the enthalpy, or change in heat energy, increases.

Examples

Ammonium chloride solid dissolves in water as follows:

• NH4Cl(s) + H2O(l) + heat → NH4Cl(aq)

Water and potassium chloride are mixed together as follows:

• KCl(s) + H2O(l) + heat → KCl(aq)
• **Photosynthesisis the process through which chlorophyll in green plants converts water and carbon dioxide into glucose and oxygen. As a result, it is the energy provider.
• When a little quantity of ammonium chloride is mixed with water in a test tube. The test tube then appears to grow cooler. As a result, heat is absorbed from the test tube's surroundings.
• Conversion of ice to water by boiling, melting, or evaporation

What is an Exothermic Reaction?

An endothermic reaction is the opposite of these processes. It will discharge energy into the environment either as heat or light. Examples include neutralization, burning something, fuel reactions, the buildup of dry ice, breathing, etc.

The terms "**exo" and "**thermic" here allude to "**release" and "**heat," respectively.

Therefore, energy is released during exothermic processes. These reactions are warmer and occasionally risky due to their fast rate responses. The creation of new bonds (products) at a higher level is what causes the energy to be released. While the energy required to dissolve the bonds between the reactants is less. At the end of the process, the enthalpy change likewise decreases. During chemical processes, a lot of energy is really needed. The connection connecting the molecules together was held together by this energy. Therefore, a significant quantity of energy is released during reactions between molecules and compounds and during the breaking of bonds.

Conclusion

Chemical reactions are classified as endothermic or exothermic based on the amount of energy transferred between the system and its surroundings. The primary distinction between endothermic and exothermic processes is that endothermic reactions collect energy from their surroundings, whereas exothermic reactions release energy into them. By determining the enthalpy change in the reaction, any chemical reaction may be classified into one of two types.

Difference between Endothermic and Exothermic Reactions