Differing compounds have bonds that can hold different quantities of energy. Each of these various molecules would retain a varied amount of energy to put it another way, each would have different quantities of energy in its chemical energy storage.
It’s important to understand that chemical bonds serve as energy storage. The kinds of bonds and the chemical species present can affect how much energy is held in the bonds, among other things. Bonds are broken and new bonds are created during chemical reactions. The total energy held in the new bonds is different from that in the initial bonds.
Therefore, some method of accounting for the difference in energy must be used. Heat energy from the environment is used in this.
The two primary roles that perform these reactions are endothermic and exothermic.
The difference between endothermic and exothermic reactions is that an endothermic reaction takes place when energy from the environment absorbs heat from the surroundings.
On the other hand, an exothermic reaction involves releasing energy from the system into the environment.
Let’s start learning the simplest definitions of endothermic and exothermic reactions:
Table of Contents
What are Exothermic Reactions?
A chemical reaction involves the transfer of energy to or from the environment, which results in a temperature change. Energy releases into the environment during exothermic reactions.
The reaction mixture and its surroundings heat up as the energy is typically transported as heat energy. A thermometer can be used to measure the temperature increase.
Exothermic reactions include the following examples:
• Burning
• A lot of oxidation reactions, such as rusting
• Acids and alkalis react to neutralize each other.
What are Endothermic Reactions?
Endothermic is a process that absorbs more heat energy than it produces because the initial ingredients have a lower enthalpy (H) value than the finished goods.
This indicates that when an endothermic reaction happens, it becomes colder. For instance, the water-ammonium nitrate solution.
The total bond enthalpy of the reactants in an endothermic reaction is higher than the total bond enthalpy of the products.
As a result, more chemical energy than heat energy is produced when new bonds form in the products, meaning that the heat energy that is received and turned into chemical energy to break the bonds in the reactants is greater.
Endothermic reactions include the following examples:
- Water evaporation
- Melting of ice
- Cooking
Read more: What is the Difference Between Work and Power?
Difference Between Endothermic and Exothermic Reaction
1. The major difference between endothermic and exothermic reactions is that net heat is emitted during exothermic reactions, but endothermic reactions require heat to be supplied.
2. Another difference between endothermic and exothermic reactions is that exothermic reaction products are typically more stable than endothermic reaction products.
3. In an endothermic reaction, more energy is stored in the newly formed bonds of the products than in the reactants’ initial bonds.
To make up for the energy discrepancy, heat energy from the environment will be absorbed during the production of the new bonds.
In essence, endo means “into” and thermic means “heat” hence heat is a factor in forming chemical bonds. We can think of heat as another reactant in terms of reactions.
Example: Heat + A + B -> AB
4. The opposing state is called exothermic. In an exothermic reaction, fewer energy stores in the original bonds of the reactants’ products than in their new bonds.
To make up for the energy differential, heat energy will be released into the environment as the new bonds form. Exo means “out of” therefore heat is produced as the chemical bonds are formed. Then, we can think of heat as a product in terms of reactions.
Example: A + B = heat + AB
How do Exothermic and Endothermic Reaction Occur?
Enthalpy change, measured at constant pressure, is the heat that enters the system from the environment while simultaneously leaving it. This is the enthalpy change of the system.
From the viewpoint of a chemist, the question is how much heat should be added to maintain a constant temperature and pressure.
The reaction is exothermic (delta H is negative / the system loses enthalpy) if the value is negative because the system loses heat to the environment.
The opposite is true for an endothermic reaction: the system absorbs heat from the environment (delta H is positive / the system gains enthalpy).
Endothermic Vs. Exothermic Graph
Endothermic vs. exothermic graph is given below with the explanation.
A reaction graph displays the evolution of a reaction’s energy. In general, an endothermic process absorbs energy from the environment if the graph’s line moves upward.
The exothermic reaction releases energy into the environment if the line falls.
In an endothermic graph products’ energy is greater than the energy of the reactants.
In an exothermic graph products’ energy is lower than the energy of the reactants.
The additional energy required when reactants with lower energy transform into products with higher energy is taken by the reactants from their environment. The process is hence endothermic.
The extra energy the reactants have is released into the environment when they shift from reactants with higher energy to products with lower energy. The reaction is hence exothermic.
As you can see from these examples, an endothermic process progresses and ends in a higher state as its potential energy rises. The graph demonstrates that the converse is true for exothermic reactions.
Endothermic And Exothermic Energy Diagram
According to the endothermic and exothermic energy diagram below, reactants are at a lower energy level in an endothermic reaction than the products.
The products are, therefore, less stable than the reactants.
The response is positive, or ΔH, meaning energy is taken from the environment.
Diagram
In an exothermic reaction, the reactants have a greater energy level than the products. The products are, therefore, more stable than the reactants.
Overall, the reaction’s ΔH is negative, meaning energy released as heat.
What are the Differences Between Endothermic and Exothermic Reactions?
Highlighting the main differences between endothermic and exothermic reactions in the following table:
| Exothermic Reaction | Endothermic Reaction |
|---|---|
| It is a process or reaction that discharges system energy, typically as heat. | It is a process or reaction whereby the system takes up heat from its environment. |
| The system releases energy into the environment. | The reaction absorbs energy from the surroundings. |
| As the reaction progresses, the surrounding environment’s temperature rises. | As the reaction progresses, the surrounding environment’s temperature decreases. |
| The reaction’s enthalpy change is negative -ΔH. | The reaction’s enthalpy change is positive ΔH. |
| Examples are making ice and rusting of iron. | Examples are melting of ice, photosynthesis, evaporation. |
Conclusion
According to the energy transfer between the system and the environment, chemical reactions divide into endothermic and exothermic reactions.
The difference between endothermic and exothermic reactions is that endothermic reactions receive energy from the environment.
Whereas exothermic reactions release energy into the environment.
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