Real Life Examples OF Exothermic Reactions: JEE Main 2025

Exothermic reactions are a vital part of chemistry, releasing energy in the form of heat or light during the reaction process. These reactions are not only crucial for JEE Main 2025 but are also commonly observed in everyday life, making them relatable and easy to understand. Examples include combustion, respiration, freezing of water, and neutralisation reactions. Understanding these real-life examples helps students connect theoretical knowledge to practical applications, enhancing their grasp of the topic. 

The JEE Main 2025 PDF on exothermic reactions provides detailed explanations, step-by-step processes, and relatable examples, making it a valuable resource for exam preparation. By exploring these reactions, students can strengthen their concepts and approach related questions with confidence.

What is Exothermic Reactions?

Exothermic is basically produced from a Greek word, ‘Exo’ meaning exterior, while ‘thermic’ means ‘heat’. In the chemical process, exothermic means heat moving outside. The exothermic reaction is a heat-generating chemical reaction. 

Exothermic reactions generally take place in different day-to-day real-life activities. Here are some of the examples of exothermic reactions:

1. Making of an Ice Cube

Making an ice cube is a process of liquid changing its state to solid. Let's check this process, starting with water. A cup of water contains a large number of small particles of H₂O molecules. Each small particle of the H₂O molecule is moving and has some amount of energy. When an ice cube tray, filled with water, is placed in a freezer, it slowly loses heat and starts to cool down to become ice cubes. Changing water into an ice cube is an exothermic reaction. 

2. Snow Formation in Clouds

Snow formation in clouds is also an exothermic reaction. Clouds come into existence from the condensation of water vapor. Some clouds have ice and there we get the heat from condensation as well as from crystallization. For exothermic reactions, it is the process that gives energy in the form of a heat body.

3. Burning of a Candle

In the case of burning a candle, the body of the candle carries paraffin, which is a hydrocarbon. When paraffin burns with the flame, it reacts with oxygen to create carbon dioxide and water. This reaction is certainly exothermic as it gives out heat to the atmosphere with the help of other products. The amount of heat released depends on the chemical reaction between the hydrocarbon and oxygen.

4. Rusting of Iron

The rusting of iron is a chemical reaction between iron & oxygen. When iron is in pure form or alloyed, rusting of iron takes place. In this process, heat gets released when iron comes in contact with oxygen. Basically, rusting is the formation of chemical substances that takes place due to the formation of moisture on the iron. For this reaction, the chemical formula goes as Fe₂O₃.xH₂O.

5. Burning of Sugar

Inside the human body, sugar is a chemical reaction. It is formed by a combination of carbon, oxygen, and hydrogen. It releases heat once it goes inside the human body, resulting in the formation of energy. The heat goes out of the human body and gets added into the atmospheric heat. This process is called an exothermic reaction. But there are a few doubts which make it an endothermic reaction. For instance, when we put sugar in a bowl and burn it with a flame, it starts generating heat. It releases a huge amount of energy which makes it an endothermic reaction. 

6. Formation of Ion Pairs 

When ions are in gaseous form, it makes interacting with water, resulting in hydrated ions. This is an exothermic process. The smaller the ion radius, the bigger is the ion charge. Consequently, ion hydration enthalpy grows larger resulting in a concentrated exothermic reaction.

7. Reaction of Strong Acid and Water

As we know that heat is necessary to break a chemical bond. For example, Hydrogen chloride consists of a hydrogen atom H and a chlorine atom Cl connected by a covalent single bond which is a diatomic molecule.

HCl (Hydrogen chlorides) is in the form of a strong acid and when it gets mixed in water, the hydrogen ion reacts with water to make a more complex reaction. Since hydrogen ions are very tiny in size and a large amount of energy that is generated gets concentrated in a relatively smaller area. At this time, it draws the polar water molecules. The hydrogen ions result in the formation of a covalent bond with water and also attract a number of strong hydrogen bonds. So, this process is an exothermic process. 

8. Water and Calcium Chloride

Calcium chloride, water, and baking soda mixed together (the experiment is done by the students in their school labs) produce a rise in the temperature by letting off heat into the atmosphere. This process is also known as an exothermic reaction.

9. Cold Packs to Heal an Injury

One other example of an exothermic reaction is a cold pack. If we apply a cold pack to the place of pain after an injury then it will be an exothermic reaction. The cold pack has two bags - an inner bag and an outer bag. The inner bag contains water in it while the outer bag has ionic salts. On pressing the cold pack, the water from the inner bag gets in touch with ionic salt and eliminates heat. Thus, the heat released to the atmosphere makes it an example of an exothermic reaction.

10. Laundry Detergent

Every time you don’t require a chemistry lab for experiments, sometimes things present around you are also useful for understanding the nature of reactions. The best example of this is the detergent powder. Simply dissolving laundry detergent in a bit of water generates heat. So, this is a process of an exothermic reaction.

11. Nuclear Fission

Nuclear fission is a unique exothermic reaction in which the nucleus of a heavy atom splits into pieces such as lighter elements and releases energy. In this process of Nuclear Fission, energy is released in the form of heat, kinetic energy, and gamma photons which is a form of high energy radiation.

Heavy atomic nuclei are bombarded with free neutrons which break the nucleus apart in nuclear reactors and bombs. As a result, the fission reaction releases more neutrons. So this is an example of an exothermic reaction.

12. Combustion Reaction

Combustion is an example of an exothermic reaction including materials like hydrocarbons reacting with oxygen to form combustion products such as water and carbon dioxide. Any combustion reaction is always involved with molecular oxygen O₂. 

For example, when wood burns, it must require the presence of O₂ and a large amount of heat is produced. Wood is one of the common combustible items that is organic (a combination of carbon, hydrogen, and oxygen). 

13. Respiration

Respiration is the process of metabolism which is common in all living things. In this process, the living organism intakes oxygen and releases carbon dioxide. Food molecules get converted into simpler substances like glucose. Then the glucose is combined with oxygen and it provides energy to our body. This is called the respiration process and respiration is an exothermic reaction. The chemical equation is shown below. 

C₆H₁₂O₆ (aq) + 6O₂ (g) 6CO₂ (g) + 6H₂O (l) +ENERGY

14. Thermite Reaction

Basically, a thermite reaction is an iron oxide (rust) reacting with aluminum to produce molten iron. The reaction is started by the formation of heat from the burning magnesium ribbon which is placed in the iron oxide/aluminum mixture. It is a mixture of iron oxide powder, aluminum powder and starts reacting when it is heated. 

This reaction is an exothermic reaction and the equation is given below. 

• Fe₂O₃ + 2Al Al₂O₃ + 2Fe

15. Neutralization Reaction 

In the process of neutralization reaction, an acid and a base react to form salt and water. Also, in this reaction, the bonds are being made and energy is released to the surroundings. 

For example The reaction between HCL (a strong acid) and NaOH (a strong base)

HCL (aq) + NaOH(aq) NaCL(aq) + H₂O(l)

The complete ionic equation is –

H₃O(aq) + CL-(aq) + Na(aq) + OH+(aq) Na+(aq) + Na+(aq) + Cl-(aq) + 2H₂O(l)

The net ionic equation is regulated by removing the spectator ions (the ions present on both the reactants and the product side) 

H₂O+ (aq) + OH-(aq) 2H₂O (l)

16. Barking Dog

It is an interesting exothermic reaction. In this reaction, you need a long glass tube, nitrous oxide and carbon disulfide. In case these chemicals are not available with you then there is an alternative solution – a bottle and rubbing alcohol. It is not as loud as the above reaction but it does produce a nice flame and an audible ‘woofing’ sound. 

17. Decomposition of Vegetable 

Decomposition of vegetables is also an exothermic reaction because microbes need the energy to break the bond of vegetables that’s why it produces heat energy. This process is largely carried out by soil invertebrate fauna and this decomposition is known as an exothermic reaction.

18. Solution of Sulfuric Acid in water

The processes of adding water into acid or acid into water are both exothermic reactions. The reason behind this is a number of possible factors, including increased entropy, as you are breaking a bond of hydrogen and chlorine atoms in hydrochloric acid, making new ions namely free chloride and hydronium. 

The dissolution takes place in the two steps mentioned below:

Step 1

H₂SO₄ + H₂O H₃O + HSO₄^-

Step 2

HSO₄^-+ H₂O H₃O⁺ + SO₄₂

What are Endothermic Reactions?

Endothermic reactions are chemical processes that absorb heat energy from their surroundings, causing the environment’s temperature to drop. In these reactions, the energy needed to break the reactants' bonds is greater than the energy released during the formation of new product bonds. This results in a net intake of energy, making the reaction feel cold to the touch.

Key Features of Endothermic Reactions:

• Heat Absorption: These reactions draw heat from the surroundings.

• Cooling Effect: The surrounding temperature decreases during the reaction.

• Positive Enthalpy Change (ΔH): A positive enthalpy value indicates that energy is absorbed.

Examples Include:

• Photosynthesis: Plants use sunlight to convert water and carbon dioxide into glucose and oxygen.

• Melting Ice: Heat is absorbed as ice changes from solid to liquid.

• Water Evaporation: Heat is taken in when water transitions from liquid to vapour.

This is how the basic illustrations below look like between Exothermic reactions and Endothermic reactions 

Check the Difference Between Exothermic and Endothermic Reactions by Vedantu. 

Other Important Key Concepts for JEE Main 2025

Understanding exothermic reactions goes beyond just recognising them in everyday life. JEE Main aspirants need to delve deeper into the thermodynamics behind these reactions. Here are some key concepts to master:

1. Enthalpy Change (ΔH): This value tells you how much heat is released or absorbed in a reaction. A negative ΔH indicates an exothermic reaction.

2. Hess's Law: This law allows you to predict the ΔH of a reaction by combining the ΔH values of simpler reactions.

3. Entropy Change (ΔS): In general, exothermic reactions tend to increase the entropy of the system, reflecting a move towards greater disorder.

4. Reaction Rates: Factors like temperature, concentration, and catalysts can affect the rate of an exothermic reaction. Higher temperatures generally increase the rate, while catalysts speed things up.

5. Equilibrium: Exothermic reactions can reach an equilibrium state where the forward and reverse reactions occur at the same rate. Understanding this concept is crucial for various JEE Main problems.

Practice Makes Perfect:

Don't just read about exothermic reactions – experience them! Here are some fun ways to explore:

• Try making your own hand warmers using magnesium and iron filings (with adult supervision, of course!).

• Conduct neutralization reactions with different acids and bases to observe the fizz and heat release.

• Build a simple model volcano using baking soda and vinegar to see the power of exothermic reactions in action.

Solved Examples with Explanations

1. Combustion of Wood:

Reaction:

$C_6H_{12}O_6(s) + 6O_2(g) \rightarrow 6CO_2(g) + 6H_2O(l) + \text{heat}$

Explanation:

The combustion of glucose (wood is primarily composed of cellulose, a glucose polymer) with oxygen produces carbon dioxide and water, releasing heat energy. This is a common example of an exothermic reaction, as it releases heat and light, seen as a burning flame.

2. Neutralization of Hydrochloric Acid with Sodium Hydroxide:

Reaction:

$HCl(aq) + NaOH(aq) \rightarrow NaCl(aq) + H_2O(l) + \text{heat}$

Explanation:

When hydrochloric acid reacts with sodium hydroxide, it forms table salt (sodium chloride) and water. This neutralization reaction is exothermic, releasing heat. It's an example of an acid-base reaction commonly encountered in chemistry.

3. Combustion of Methane

Reaction:

$CH_4(g) + 2O_2(g) \rightarrow CO_2(g) + 2H_2O(g)$

Explanation:

When methane (a component of natural gas) reacts with oxygen, it produces carbon dioxide and water. This is a classic example of combustion, and it releases energy in the form of heat.

4. Formation of Table Salt

Reaction:

$Na(s) + Cl_2(g) \rightarrow 2NaCl(s)$

Explanation:

When sodium reacts with chlorine gas, table salt (sodium chloride) is formed. This reaction is exothermic, meaning it releases energy.

5. Formation of Water

Reaction:

$2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$

Explanation:

When hydrogen gas reacts with oxygen gas, water is formed. This reaction releases a significant amount of energy, making it an exothermic process.

Conclusion

Exothermic reactions are not just abstract concepts; they are the driving force behind many everyday phenomena. Through the study of reactions that release energy in the form of heat, such as combustion, neutralization, and biological processes like respiration, By understanding them, you'll not only crack your JEE Main Chemistry but also gain a deeper appreciation for the invisible forces shaping our everyday lives.

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