Changes Around Us

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Everyday we encounter differing 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.


So Many Changes

Reversible Change

Reversible change is that change that can be reversed by one or more methods. Usually, there is a change in 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.


Change

Any difference in the size or shape of an object is referred to as a change.

Changes are either reversible or irreversible.


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.


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 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 changes 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 decrease in temperature. This means that as the temperature decreases from 4°C to 0°C, water expands. This behaviour is called 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 or an impure substance are carried out with the following purposes :

To remove the unuseful or harmful component.

  1. To obtain the useful component.

  2. To remove impurities for getting a pure sample.

FAQ (Frequently Asked Questions)

Q1. Define Changes Around Us.

Ans: Everyday 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.

Q2. What is Expansion and Contraction?

Ans: 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 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 changes 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.

Q3. What are the 2 Types of Changes?

Ans:

Reversible Change

Reversible change is that change that can be reversed by one or more methods. Usually, there is a change in 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.


Change

Any difference in the size or shape of an object is referred to as a change.

Changes are either reversible or irreversible.


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.