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.
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.
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
Burning paper and wood, weathering rocks, rusting iron, and other irreversible processes are examples. A permanent change is an irrevocable change.
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.
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.
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.
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
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.
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.
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.
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.
FAQs on Changes Around Us
1. What is a reversible change? Provide some examples.
A reversible change is a temporary change that can be undone or reversed, meaning the substance can return to its original form. These changes usually affect the physical properties like shape, size, or state. Common examples include:
- Melting of ice into water, which can be frozen back to ice.
- Folding a piece of paper, which can be unfolded.
- Stretching a rubber band, as it returns to its original size.
- Inflating a balloon, as it deflates back to its original shape.
2. What is an irreversible change? Can you give some examples?
An irreversible change is a permanent change that cannot be undone by simple physical means. In most irreversible changes, a new substance with different properties is formed. Examples include:
- Burning of wood or paper, which turns into ash.
- Cooking an egg, which permanently changes its texture and chemical makeup.
- The rusting of iron, where iron turns into a new substance called iron oxide.
- The ripening of a fruit.
3. What is the main difference between a physical and a chemical change?
The main difference lies in whether a new substance is formed. A physical change alters the form or appearance of a substance but not its chemical identity, like melting ice into water. It is often reversible. In contrast, a chemical change results in the formation of one or more entirely new substances with different properties, such as when wood burns and becomes ash. This type of change is always irreversible.
4. How does heating and cooling cause expansion and contraction in materials?
Heating and cooling cause changes by affecting the tiny particles that make up a substance.
- Expansion: When a substance is heated, its particles gain energy, move faster, and spread apart. This makes the substance take up more space, or expand.
- Contraction: When a substance is cooled, its particles lose energy, slow down, and move closer together. This makes the substance take up less space, or contract.
5. Why is melting an ice cube considered a reversible change, but burning a piece of paper is irreversible?
Melting an ice cube is a reversible, physical change because only the state of water changes from solid to liquid. The substance is still water (H₂O) and can be frozen back into ice. Burning paper is an irreversible, chemical change because the paper reacts with oxygen to produce entirely new substances like ash, carbon dioxide, and water vapour. These new substances cannot be converted back into paper.
6. Can a single event involve both a reversible and an irreversible change? Explain with an example.
Yes, a single event can involve both types of changes. A burning candle is a perfect example. The melting of the wax near the flame is a reversible, physical change because the melted wax can cool and become solid again. However, the burning of the wick and wax vapour to produce light and heat is an irreversible, chemical change, as it creates new substances like soot and carbon dioxide.
7. What is the anomalous expansion of water and why is it important for aquatic life?
Anomalous expansion of water is its unusual behaviour of expanding when cooled below 4°C. Most substances contract continuously when cooled. Water contracts until it reaches 4°C, but then it begins to expand as it cools further to 0°C to become ice. This makes ice less dense than water, causing it to float. This property is crucial for aquatic life because lakes and rivers freeze from the top down, creating an insulating layer of ice that protects the water below from freezing solid, allowing fish and other organisms to survive the winter.
8. A potter shapes clay into a pot, bakes it, and then the pot accidentally breaks. Identify the reversible and irreversible changes in this process.
This process demonstrates different types of changes:
- Reversible Change: Shaping the wet clay into a pot. This is a physical change of shape that can be undone by adding water and reforming the clay.
- Irreversible Change (Chemical): Baking the pot in an oven. The intense heat causes permanent chemical reactions in the clay, making it hard and strong. This change cannot be reversed.
- Irreversible Change (Physical): The pot breaking into pieces. Although the material is still baked clay, it has undergone a permanent change in form that cannot be easily undone.
