Difference between Endothermic and Exothermic Reactions

This topic is for explaining the difference between Endothermic and Exothermic Reactions. In chemistry, we also can categorize the reactions as endothermic and exothermic reactions. This is on the basis of release or taking the energy in the form of sound, light, cold, or heat. In an easy way, the endothermic reactions absorb energy from the surrounding, which is in the form of heat. Whereas, an exothermic reaction releases the energy into the surrounding of the system. Photosynthesis is a popular example of an endothermic chemical reaction. During this process, plants absorb energy from the Sun. One popular example of an exothermic reaction is the chemical reaction between sodium and chlorine, which results in common salt i.e. sodium chloride. Let us have a detailed study about the difference between Endothermic and Exothermic Reactions.

What is Endothermic Reaction?

The endothermic process is a term which describes a chemical reaction where the system absorbs the heat energy from its surrounding. Some such examples are evaporating liquids, melting ice, dry ice, alkanes cracking, thermal decomposition, etc. As its name suggests that ‘endo‘ means ‘to absorb’ and ‘thermic‘ means ‘heat’.

Thus, one can define the endothermic reactions as a chemical reaction where the energy is absorbed. This energy is due to the conversion of reactants into the product. It is happening due to the dissociation of the bonds between the molecules. Then, the energy is released, with the formation of new bonds.

In such reactions, the heat is taken up from the surroundings, and hence the temperature of the system where the reaction is going remains cooler. Also, the enthalpy which is the change in heat energy during the conversion of reactants to the products becomes higher at the end of the reaction.

What are Exothermic Reactions?

These reactions are the opposite of an endothermic reaction. It will release the energy by light or heat into the surrounding. Some examples are neutralization, burning a substance, reactions of fuels, deposition of dry ice, respiration, etc, Here the term ‘Exo‘ refers ‘to release’, and ‘thermic‘ refers to the ‘heat’. So, exothermic reactions are involving the release of energy. These types of reactions are warmer, and sometimes they may be dangerous with high rate reactions.

The released energy is due to the formation of new bonds (products) at a higher level. While the energy of breaking up the bonds (reactants) is at a lower level. The enthalpy change also becomes lower at the end of the reaction. Actually, there is a lot of energy requirements during chemical reactions. This energy was used to hold the bond holding the molecules together. So with the reactions between molecules and compounds, with the breaking of bonds, a huge amount of energy release.

Difference between Endothermic and Exothermic Reactions

The important difference between Endothermic and Exothermic Reactions

Parameter	Endothermic Reactions	Exothermic Reactions
Meaning	These are involving the use of energy at the time of dissociation to form a new chemical bond.	These are involving the release of in the form of heat.
Energy	The process requires energy in the form of heat.	The process evolves energy in the form of heat.
Enthalpy	Enthalpy is positive, as heat is absorbed.	Enthalpy is negative, as heat is evolved.
Examples	Melting ice, evaporation, cooking, gas molecules, photosynthesis are few examples	Rusting iron, settling, chemical bonds, explosions, nuclear fission are a few examples.

Some examples:

After seeing the difference between Endothermic and Exothermic Reactions, let us have some categories of reactions. First of Exothermic kind:

1. Combustion – Burning of coal, a candle, and sugar.
2. When the detergent dissolves in water, or while adding water to the quicklime during whitewash. In such a reaction, there is the production of ample heat, which warms up the water.
3. Formation of ice from water.
4. Respiration, digestion of food.

Some categories of reactions of Endothermic kind:

1. Photosynthesis – In this process, chlorophyll present in green plants in converted the water and carbon dioxide into the glucose and oxygen. And hence it is the energy provider.
2. When the small amount of ammonium chloride is taken in a test tube with water. Then we can see that the test tube becomes colder. So, heat is absorbed from the surrounding means test tube.
3. Conversion of ice into the water through boiling, melting, or evaporation.

FAQs on Exothermic and Endothermic reactions:

Q.1: What will happen with the rate of an exothermic reaction, due to an increase in temperature?

Answer: The rate of a reaction always increases with the temperature. So, don’t confuse the rate at which a reaction proceeds with the final equilibrium of the reaction.

Q.2: What type of energy conversion will occur during the endothermic reaction?

Answer: This is kinetic energy to chemical energy. In the endothermic reaction, heat is absorbed and then converted into chemical energy. Note that the temperature is the measure of heat, and it is not energy in itself.