Reversible and Irreversible Changes - Definition, Examples, Difference, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:49 PM IST

Changes are the fundamental activity of the environment, all around there are changes that are continuously happening. Among the changes that happen around us, we can classify them into reversible and irreversible changes.

What is Reversible change?

Reversible changes are the changes that can be reversed back to the original.

What is Irreversible change?

Irreversible changes are changes that cannot be reversed back to the original.

Reversible and irreversible changes example

examples of reversible change

Melting: Melting is the process, when solid substances convert into a liquid after heating. An example of melting is the conversion of ice into water.
Freezing: Freezing is the process, through which a liquid converts into a solid. An example of freezing is the conversion of water into ice.
Boiling: Boiling is the process through which a liquid converts into a gas. An example of boiling is the conversion of water into water vapour.

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This Story also Contains

What is Reversible change?
What is Irreversible change?
Examples of Reversible Change
Difference Between Reversible and Irreversible Changes
What are Physical changes
Irreversible change:-

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Examples of Reversible Change

Straight wire to coiled wire.

Melting of coal tar.

Folding of dresses (shirts etc)

Moulding of wet clay into pot on potter’s wheel

Softening of iron on heating and changes to red hot stage.

Reversible and irreversible changes

Difference Between Reversible and Irreversible Changes

Process of Burning: When we burn a piece of paper or wood, then it will turns to ash and smoke. We will not be able to obtain paper and wood from the ash again.
Process of Cooking: We generally use heat energy for cooking, and once we cook our eggs, we cannot uncook them. That’s why, we can say cooking as an irreversible change.
Rusting of iron: You must have seen a rusted piece of iron. When water vapour (humidity) comes in contact with the iron, then it reacts and forms an iron water complex that we call rust. We cannot reverse back this process of rusting, so that rusting of iron is also known to be an irreversible change.

Any changes that can be reversed or at a temporary conversion is known as reversible changes. All the reactions that can be reversed back are referred to as reversible reactions. Some of the Processes like melting, boiling, evaporation, freezing, condensation, dissolution are generally acted as reversible changes. Some examples of reversible changes are freezing of ice, melting of wax, vapours formed during evaporation.

Reactions result in interaction between two or more compounds called reactants to form a product. In a reversible reaction, reactants and products that are formed are connected by a two-way arrow (⇌). This means that reactants can be obtained back from the products.

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The equation to show reversible reaction is given below,

A +B ⇌ C + D

Here you can see that two reactants A and B react with each other to form products C and D. Here, the two-headed arrow denotes that the reaction is reversible. Here, the reactant can be obtained back from C and D.

In comparison with reversible changes, irreversible changes are known to be permanent changes. Reactants react with each other to form an entirely new compound and the product formed cannot be able to reverse. Heating, burning, mixing, powdering are some of the processes which led to irreversible changes. A common and observable household example is the cooking of raw eggs and they can’t be formed back to the raw form. On burning paper ash is formed which cannot be converted back, it is another example of irreversible change.

If any reaction takes place in a unidirectional way, the reaction is known as an irreversible reaction. In such types of reactions, within a period of time, they react completely to form a product. And this type of reaction is denoted with the help of a one-way arrow (→).

F representation,

A → B +C

Here, A is the reactant that is completely converted into products B and C and we cannot be able to get back the reactant A.

Some key points regarding reversible changes are:-

A reversible change is a form of chemical change in which no new materials are going to be created and the original material can be recovered by backward reaction. A common example of reversible reaction is freezing of water to make ice or melting of chocolate.

In this change, substances can be changed back to their original state.

The chemical properties of the substance will not be affected.

We can also observe that most of the physical changes are also reversible changes.

What are Physical changes

Physical changes are the changes that will cause changes in the physical properties of any substance, like change in shape, change in size, and nature. Physical changes may be or may not be reversible but in many cases physical changes are reversible. For example conversion of water into ice is a general example of reversible changes whereas growth in height is an irreversible change.

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Q- Give two Examples of Reversible Change ?

Melting of wax.

Stretching of a rubber band.

Stretching of a spring.

Inflation of a balloon.

Ironing of clothes.

Folding of paper.

Rolling a chapati (roti) from dough.

Dissolving salt in water.

Dissolving sugar in water.

Knitting of sweater (woollen yarn to knitted sweater).

Melting of ice candy.

Melting of ice cream (solid ice cream to molten ice cream).

Drying of clothes (wet clothes to dry clothes)

Heating of milk (cold milk to hot milk)

Expansion of metals on heating.

Straight wire to coiled wire.

Melting of coal tar.

Folding of dresses (shirts etc)

Moulding of wet clay into pot on potter’s wheel

Softening of iron on heating and changes to red hot stage.

Irreversible change:-

An irreversible change is the one in which a product cannot be changed back to its original form. Generally in most of the irreversible changes, new materials are going to be formed. A substance cannot be able to returns back into its former state

The chemical properties of respective substances will be changed.

All chemical changes are also irreversible changes.

Q- Some examples of irreversible changes ?

Process of Burning: When we burn a piece of paper or wood, then it will turns to ash and smoke. We will not be able to obtain paper and wood from the ash again.
Process of Cooking: We generally use heat energy for cooking, and once we cook our eggs, we cannot uncook them. That’s why, we can say cooking as an irreversible change.
Rusting of iron: You must have seen a rusted piece of iron. When water vapour (humidity) comes in contact with the iron, then it reacts and forms an iron water complex that we call rust. We cannot reverse back this process of rusting, so that rusting of iron is also known to be an irreversible change.

We can also observe that many of the chemical changes are irreversible.

Q- What is a chemical change?

The changes where the chemical properties of the compound change like flammability, radioactivity. All chemical changes are referred to as irreversible changes. As the chemical properties of the substance are changed, the original compound is not returned back.

10 Examples of irreversible changes

burning of paper,

Burning of fuels (like Wood, Coal and LPG),

Cooking of food,

Rusting of iron ,

Grinding of wheat grains into flour,

Baking of chapati (roti),

Growth of a plant,

Formation of flower from bud,

Falling of leaves from a tree,

Ripening of fruits,

Ageing of human beings.

Chemical changes are reversible or irreversible

Chemical changes are irreversible changes as in chemical change the chemical properties of the compound is changed that cannot be reversed back.

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Frequently Asked Questions (FAQs)

1. How does an irreversible change differ from a reversible change?

An irreversible change is a process where the original substance cannot be recovered from the products by simple means. Once the change occurs, it's difficult or impossible to return to the initial state. Irreversible changes are typically associated with chemical reactions that go to completion.

2. What is the role of catalysts in reversible reactions?

Catalysts increase the rate of both forward and reverse reactions in a reversible process without being consumed. They do not affect the position of equilibrium but help the system reach equilibrium faster by lowering the activation energy for both directions of the reaction.

3. Can a chemical reaction be both reversible and irreversible?

While it may seem contradictory, some reactions can be considered both reversible and irreversible depending on the conditions. For example, the combustion of hydrogen is typically irreversible under normal conditions, but at very high temperatures, it can become reversible to some extent.

4. What is the significance of reversible reactions in biological systems?

Reversible reactions are crucial in biological systems as they allow for fine-tuning of metabolic processes. They enable cells to respond quickly to changes in their environment by shifting the equilibrium of reactions. Examples include the binding and release of oxygen by hemoglobin and many enzyme-catalyzed reactions.

5. How does the concept of entropy relate to reversible and irreversible changes?

Entropy, a measure of disorder in a system, generally increases in irreversible processes. In reversible processes, the entropy change of the system and surroundings sum to zero. Irreversible processes always lead to an increase in the total entropy of the universe.

6. Can you provide examples of reversible changes in everyday life?

Some common examples of reversible changes include:

7. What role do reversible reactions play in energy storage systems?

Reversible reactions are fundamental to many energy storage systems. For example, in rechargeable batteries, the charging process reverses the chemical reactions that occur during discharge. This reversibility allows for repeated cycles of energy storage and release, making these systems efficient for storing renewable energy.

8. How do buffer solutions demonstrate the principles of reversible reactions?

Buffer solutions exemplify reversible reactions in action. They consist of a weak acid or base and its conjugate, which can reversibly accept or donate protons. This reversibility allows buffers to resist changes in pH when small amounts of acid or base are added, maintaining a relatively stable pH in biological and chemical systems.

9. How do reversible reactions contribute to the concept of chemical potential?

Chemical potential is a key concept in understanding the behavior of reversible reactions. In a system at equilibrium, the chemical potentials of all components are equal. This equality drives the distribution of substances between phases and determines the direction of spontaneous processes, making it fundamental to predicting and controlling reversible reactions.

10. What is the relationship between Le Chatelier's Principle and reversible reactions?

Le Chatelier's Principle is a fundamental concept for understanding reversible reactions. It states that when a system at equilibrium is subjected to a change in concentration, temperature, volume, or pressure, the system will adjust to counteract that change. This principle helps predict how reversible reactions will respond to changes in conditions.

11. What are some examples of irreversible changes?

Examples of irreversible changes include:

12. How do reversible reactions impact the efficiency of fuel cells?

Reversible reactions are crucial for the efficiency of fuel cells. The ideal fuel cell operates reversibly, converting chemical energy to electrical energy with minimal waste. However, real fuel cells experience irreversibilities that reduce efficiency. Understanding and minimizing these irreversibilities is key to improving fuel cell performance.

13. What is the difference between kinetic and thermodynamic reversibility?

Kinetic reversibility refers to the ability of a reaction to proceed in both forward and reverse directions at measurable rates. Thermodynamic reversibility, on the other hand, is an idealized concept where a process can be reversed with no increase in entropy. Real processes are often kinetically reversible but thermodynamically irreversible.

14. How does the concept of Gibbs free energy relate to reversible and irreversible processes?

Gibbs free energy (G) is a thermodynamic potential that indicates the spontaneity of a process. In reversible processes, the change in Gibbs free energy (ΔG) is zero at equilibrium. For irreversible processes, ΔG is negative for spontaneous reactions and positive for non-spontaneous reactions.

15. How do reversible and irreversible processes relate to the laws of thermodynamics?

The laws of thermodynamics govern both reversible and irreversible processes. The second law of thermodynamics states that the total entropy of an isolated system always increases for irreversible processes, while it remains constant for reversible processes. This fundamental principle underlies the distinction between these two types of processes.

16. How does the concept of reversibility apply to phase changes?

Phase changes, such as melting, freezing, vaporization, and condensation, are typically reversible processes. They involve changes in the physical state of matter without altering its chemical composition. The reversibility of these processes is crucial in many applications, from refrigeration cycles to the water cycle in nature.

17. How does the concept of reversibility apply to adsorption processes?

Adsorption, the adhesion of molecules to a surface, often involves reversible processes. The adsorption and desorption of gases on solid surfaces can be reversible under certain conditions. This reversibility is crucial in applications such as gas storage, catalysis, and purification processes, where the ability to release adsorbed molecules is as important as the adsorption itself.

18. How does the concept of reversibility apply to polymer chemistry?

In polymer chemistry, reversibility plays a role in various processes. Some polymerization reactions are reversible, allowing for the breakdown of polymers under certain conditions. This is important in the development of recyclable and biodegradable plastics. Additionally, reversible cross-linking in some polymers enables self-healing materials and shape-memory polymers.

19. What role do reversible reactions play in the carbon cycle?

Reversible reactions are integral to the carbon cycle. For example, the dissolution of CO2 in water and its conversion to carbonic acid is a reversible process. This reversibility allows for the exchange of CO2 between the atmosphere and oceans, playing a crucial role in regulating atmospheric CO2 levels and ocean acidity.

20. What is the importance of reversible reactions in atmospheric chemistry?

Reversible reactions are crucial in atmospheric chemistry, particularly in the formation and dissociation of various compounds. For example, the formation of ozone in the stratosphere and its breakdown is a reversible process influenced by solar radiation. Understanding these reversible reactions is key to modeling and predicting atmospheric phenomena and climate change.

21. What is hysteresis, and how does it relate to reversible processes?

Hysteresis is a phenomenon where the state of a system depends on its history. In the context of reversible processes, hysteresis occurs when the forward and reverse paths of a process don't exactly coincide. This can lead to energy losses and is often observed in materials science, particularly in magnetic and elastic materials.

22. Can you explain the concept of microscopic reversibility?

Microscopic reversibility is a principle stating that, at equilibrium, any molecular process and its reverse must occur at the same rate. This ensures that there is no net flow of matter or energy in any direction, maintaining the equilibrium state at the molecular level.

23. What is the importance of understanding reversible reactions in green chemistry?

Understanding reversible reactions is crucial in green chemistry for developing sustainable processes. Reversible reactions allow for the recycling of reactants and the design of closed-loop systems, reducing waste and improving atom economy. They also enable the use of milder reaction conditions, contributing to more environmentally friendly chemical processes.

24. How does the concept of reversibility apply to nuclear reactions?

While most nuclear reactions are irreversible under normal conditions, some nuclear processes exhibit a form of reversibility. For example, in nuclear magnetic resonance (NMR), the alignment of nuclear spins in a magnetic field is a reversible process. Understanding these reversible aspects is crucial in applications like medical imaging and materials analysis.

25. What is the significance of reversible reactions in the field of green solvents?

In the development

26. What is a reversible change in chemistry?

A reversible change is a process where the original substance can be recovered from the products by simple means. In these reactions, the products can be converted back into the reactants under suitable conditions. This type of change is often associated with physical changes and some chemical reactions that reach equilibrium.

27. How does temperature affect reversible reactions?

Temperature can significantly impact reversible reactions by shifting the equilibrium. In endothermic reactions, increasing temperature favors the forward reaction, while in exothermic reactions, decreasing temperature favors the forward reaction. This principle is known as Le Chatelier's Principle.

28. How does pressure influence reversible reactions involving gases?

In reversible reactions involving gases, pressure can shift the equilibrium. According to Le Chatelier's Principle, increasing pressure favors the reaction that produces fewer gas molecules, while decreasing pressure favors the reaction that produces more gas molecules.

29. What is meant by "dynamic equilibrium" in reversible reactions?

Dynamic equilibrium is a state in a reversible reaction where the forward and reverse reactions occur at the same rate, resulting in no net change in the concentrations of reactants and products. Although there's no macroscopic change, the reactions continue to occur at the molecular level.

30. How do reversible reactions contribute to chemical equilibrium?

Reversible reactions are the foundation of chemical equilibrium. As the forward and reverse reactions proceed, they eventually reach a point where their rates are equal, establishing equilibrium. This dynamic state allows systems to maintain stability while still being responsive to changes in conditions.

31. What is the significance of reversible reactions in electrochemistry?

In electrochemistry, reversible reactions are fundamental to the operation of batteries and fuel cells. The ability of electrochemical reactions to proceed in both directions allows for the charging and discharging of batteries. The degree of reversibility also affects the efficiency and lifespan of electrochemical devices.

32. How do reversible reactions contribute to homeostasis in biological systems?

Reversible reactions are essential for maintaining homeostasis in biological systems. They allow for rapid adjustments in response to changes in the cellular environment. For example, the reversible binding of oxygen to hemoglobin enables efficient oxygen transport and delivery, adapting to varying oxygen concentrations in different tissues.

33. What is the role of reversible reactions in analytical chemistry techniques?

Reversible reactions are crucial in many analytical chemistry techniques. For instance, in titrations, the endpoint often involves a reversible color change of an indicator. In chromatography, the reversible adsorption and desorption of compounds on the stationary phase allow for separation. Understanding these reversible processes is key to accurate analysis and method development.

34. How do reversible reactions contribute to the function of enzymes?

Enzymes often catalyze reversible reactions, allowing them to function in both synthetic and degradative pathways. The reversibility of enzyme-catalyzed reactions enables fine control of metabolic processes, as the direction of the reaction can be influenced by substrate and product concentrations. This reversibility is crucial for maintaining cellular homeostasis and adapting to changing metabolic needs.

35. What is the significance of reversible reactions in chemical engineering processes?

In chemical engineering, understanding reversible reactions is crucial for process design and optimization. Many industrial processes, such as the Haber process for ammonia production, involve reversible reactions. Engineers must consider factors like temperature, pressure, and catalysts to shift the equilibrium and maximize yield while minimizing energy consumption.

36. What role do reversible reactions play in the development of smart materials?

Reversible reactions are key to the function of many smart materials. For instance, thermochromic materials change color reversibly with temperature changes, while shape-memory alloys can revert to their original shape after deformation. These materials rely on reversible molecular or structural changes, enabling them to respond to environmental stimuli in a controlled and repeatable manner.

37. How do reversible reactions contribute to the concept of chemical clocks?

Chemical clocks, or oscillating reactions, often involve a series of reversible steps that lead to periodic changes in concentration or color. The reversibility of these reactions allows the system to cycle between different states, creating observable oscillations. Understanding these reversible processes is crucial for studying non-linear dynamics and self-organization in chemical systems.

38. What is the importance of reversible reactions in drug delivery systems?

Reversible reactions play a significant role in drug delivery systems. For example, pH-sensitive polymers used in targeted drug delivery rely on reversible protonation reactions. The reversible binding of drugs to carrier molecules can also be used to control drug release rates. Understanding these reversible processes is key to designing effective and controlled drug delivery mechanisms.

39. How does the concept of reversibility apply to supramolecular chemistry?

Reversibility is a cornerstone of supramolecular chemistry, which deals with the assembly of molecules through non-covalent interactions. The reversible nature of these interactions allows for dynamic and responsive systems. This is crucial in applications like molecular recognition, self-assembly, and the development of molecular machines.

40. What is the role of reversible reactions in photochemistry?

In photochemistry, many reactions initiated by light absorption are reversible. This reversibility is crucial in processes like photosynthesis, where light energy is converted to chemical energy through a series of reversible steps. Understanding these reversible photochemical reactions is also important in the development of photochromic materials and solar energy conversion technologies.

41. How do reversible reactions contribute to the function of molecular switches?

Molecular switches rely on reversible reactions to toggle between two or more stable states. These switches can be activated by various stimuli such as light, pH, or electrical potential. The reversibility of these reactions allows for repeated switching, which is essential in applications like data storage, smart materials, and molecular computing.

42. What is the significance of reversible reactions in coordination chemistry?

In coordination chemistry, many ligand exchange reactions are reversible. This reversibility is crucial for the function of metal complexes in catalysis, where the ability to bind and release substrates is essential. It also plays a role in the color changes of transition metal complexes and in the development of sensors based on metal-ligand interactions.

43. How does the concept of reversibility apply to crystal growth and dissolution?

Crystal growth and dissolution are often reversible processes. The reversibility allows for the fine control of crystal size and shape, which is crucial in industries like pharmaceuticals and electronics. Understanding the reversible nature of these processes is key to developing methods for growing high-quality crystals and controlling crystallization in manufacturing.

44. What role do reversible reactions play in the development of self-healing materials?

Self-healing materials often rely on reversible reactions to repair damage. For example, some polymers use reversible cross-linking reactions that can reform broken bonds. The reversibility of these reactions allows the material to repeatedly heal itself, extending its lifespan and maintaining its properties over time.

45. How do reversible reactions contribute to the function of ion-selective electrodes?

Ion-selective electrodes rely on reversible ion exchange reactions at the electrode-solution interface. The reversibility of these reactions allows for continuous and accurate measurement of ion concentrations. Understanding these reversible processes is crucial for developing sensitive and selective electrochemical sensors.

46. What is the importance of reversible reactions in the field of nanotechnology?

In nanotechnology, reversible reactions are crucial for the assembly and disassembly of nanostructures. They allow for the creation of dynamic and responsive nanomaterials. For example, reversible host-guest interactions are used in the development of molecular machines and nanocarriers for drug delivery.

47. How does the concept of reversibility apply to phase-change materials?

Phase-change materials rely on reversible phase transitions, typically between solid and liquid states. The reversibility of these transitions allows these materials to store and release large amounts of energy as latent heat. This property is crucial in applications like thermal energy storage and temperature regulation in buildings.

48. What role do reversible reactions play in the development of rechargeable batteries?

Rechargeable batteries fundamentally rely on reversible electrochemical reactions. The ability to reverse the chemical reactions that occur during discharge allows the battery to be recharged and used multiple times. Understanding and optimizing these reversible reactions is key to improving battery life, capacity, and charging speed.

49. How do reversible reactions contribute to the concept of dynamic combinatorial chemistry?

Dynamic combinatorial chemistry relies on reversible reactions to generate libraries of compounds that can adapt to external stimuli or binding targets. The reversibility allows the system to continuously reorganize, potentially discovering new molecules or optimizing binding interactions. This approach is valuable in drug discovery and materials science.