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

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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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.

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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• NCERT Exemplar Class 11th Chemistry Solutions
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NCERT Chemistry Notes:

• NCERT Notes Class 11th Chemistry
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• NCERT Notes For All Subjects