Examples and Explanation of Reversible and Irreversible Changes

Every day, we encounter different types of changes. Turning day into night, night into each day, rising and setting of sun and moon, changing of climate, melting of ice, and much more. These changes occur during a minute or take an extended time. Few changes are not even noticeable.


Introduction to Changes Around Us

Substances can transform into various types. Some alterations are reversible. In such circumstances, the changed substance reverts to its original state. Other modifications are irreversible. the fabric has been permanently tampered with. A change of shape is one of the foremost basic kinds of change. Clay, as an example, could also be formed into various shapes then molded back to their original shapes. Twisted, squished, bent, or stretched materials will be used. Other solids are difficult to mold.


Because rock is extremely hard, it can not be twisted or sculpted by humans. In some cases, though, extremely high temperatures and immense pressure can alter the form of rocks. Heat may be a typical way of changing the state of a substance. Cooling can undo a number of these alterations, but others are permanent. This can be determined by the qualities of the fabric being heated and cooled.


Types of changes

Any difference in the size or shape of an object is referred to as a change. Changes are either reversible or irreversible.


  1. Reversible Change

Reversible change is that change that can be reversed by one or more methods. Usually, there is a change in the physical properties, shape, and size of the material. Mostly a replacement substance isn't formed during a reversible change. For eg: Paper folding, spring elongation, etc.


Water undergoes a variety of reversible modifications because it is heated and cooled. Once you heat ice, it melts and turns into liquid water. Further heating converts the liquid to a gas called vapor. When the vapor is cooled, it becomes liquid water again. The liquid water will intercommunicate ice because it cools further.


Other reversible changes include: -Inflating a balloon: After emptying, the balloon returns to its original shape. When an electrical bulb is shifted, it returns to its previous state of darkness.


Plastic could be a substance that will be heated to almost any temperature and shaped into practically any shape. When plastic is recycled, it undergoes a reversible transformation. Its original shape, like that of a bottle or a food storage container, is altered and transformed into something else. Clothing, outdoor furniture, and playground equipment can all be made of recycled plastic. The recycled plastic may be repurposed as a bottle or container.


From the previous statement, we will deduce that the alterations will be undone or reversed. As a result, we will define a reversible change as a transient change.


  1. Irreversible Change

The change which is permanent and can't be undone by any physical or chemical means is called an irreversible change. Formation of the latest substance is involved during this change. For example, the burning of a candle is an irreversible change as we cannot revisit the candle once burnt.


When a bit of paper is burned, it turns to ash. It's impossible to show it back on paper. When food is cooked, it always goes through an irreversible transformation. The feel, shape, fragrance, and appearance of an egg are all altered when it's fried. A permanent change has occurred as a result of the warmth.


Examples of changes

  1. Burning paper and wood, weathering rocks, rusting iron, and other irreversible processes are examples. A permanent change is an irrevocable change.

  2. When two or more compounds are mixed together, they'll change and sometimes generate a replacement material. a number of these modifications are reversible, while others are permanent.

  3. The addition of sugar to water creates a reversible combination. When sugar crystals are mixed into water, they dissolve or break apart. The water during this mixture evaporates when heated, leaving the sugar crystals behind.


  1. Chemical changes

Chemical alterations occur when a substance's chemical qualities, like flammability and radioactivity, change. All chemical transformations are irreversible. When a material's chemical properties are altered, it transforms into a special substance. As a result, it's unable to return to its previous state. The formation of the latest chemicals is stated as a chemical transformation. A replacement substance with distinct properties is generated as a result of this transformation. The molecules of the first material undergo modifications, leading to the formation of recent molecules. Here are some instances of chemical transformations.


  1. Physical changes

A phase transition is defined as a change within the shape, size, appearance, or status of a substance. There's no new substance generated as a result of this transformation. A physical alteration is typical.


So Many Ways to Change

  1. Expansion and Contraction

  • The particle of a substance expands or becomes loose when the temperature increases. When this happens, the material is said to undergo expansion.

  • When the temperature decreases, the particles of the substance contract or become tight. When this happens, the material is said to undergo contraction.

  • The amount of expansion or contraction varies in solids, liquids, and gases.

  • There are physical changes that take place when a substance or material moves from one state of matter to another.

  • Water is a classic example as it can exist as either solid, liquid, or gas.

  • Water at very low temperatures exists as a solid referred to as ice. On applying heat or increasing the temperature, the ice ‘melts’ to form water. The phase change when a solid change to liquid is named melting.

  • If we keep increasing the temperature, the water now starts to boil until it fully becomes water vapour. The physical change when a liquid changes to gas is called evaporation.

  • To get back the water from water vapour, it is possible by condensation – a physical change where the gas changes to a liquid. This is possible by lowering the temperature.


  1. Anomalous Expansion of Water

Water on cooling contracts up to 4°C. On further cooling, up to 0°C, water expands instead of contracting with a decrease in temperature. This means that as the temperature decreases from 4°C to 0°C, water expands. This behaviour is called the anomalous expansion of water.


  1. Burning

Burning is an irreversible change where a substance burns to supply new material. These new materials are ash and some gases.


For example, paper is burnt to supply ash which is different from paper in terms of appearance and properties.


  1. Separation

The separation of the components of a mixture of an impure substance is carried out with the following purposes :

  • To remove the unuseful or harmful component.

  • To obtain the useful component.

  • To remove impurities for getting a pure sample.


These are the different types of changes that happen around us. Focus on the type of change and learn its examples. Identify the differences between these changes to determine which one is what easily.


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FAQs on Changes Around Us

1. Define Changes Around Us.

Every day we encounter different types of changes. Turning day into night, night into each day, rising and setting of sun and moon, changing of climate, melting of ice, and much more. These changes occur during a minute or take an extended time. Few changes are not even noticeable.

2. What is Expansion and Contraction?

The particle of a substance expands or becomes loose when the temperature increases. Hence, the material is said to undergo expansion. When the temperature decreases, the particles of the substance contract or become tight. Hence, the material is said to undergo contraction.


The amount of expansion or contraction varies in solids, liquids, and gases. There are physical changes that take place when a substance or material moves from one state of matter to another. Water is a classic example as it can exist as either solid, liquid, or gas. It shows exceptional contraction and expansion when cooled or heated.

3. Define the differences between physical and chemical changes. Give specific examples.

i. Physical change: 

A temporary change in which the chemical composition of the substance does not change and no new substance is formed is referred to as physical change. 

  • Only the physical qualities of a substance change during a physical transformation.

  • It's a change that can be reversed. For example, when the ice melts, the water transforms from a solid to a liquid state. It's possible to re-solidify it. In both circumstances, the water remains water.

ii. Chemical change:

A chemical change is a long-term change that affects not only physical but also chemical properties. It's a change that can't be reversed. For instance, the formation of rust is a chemical change.