Current Affairs 6th Class

Changes Around

Category : 6th Class

Changes Around Us

 

Changes Around Us

We observe changes around us all the time. Changes may occur in shape, size, mass, density, colour, position, temperature, structure or in composition of a substance. So we can define a change as:

'Transformation in one or more than one physical or chemical properties of a substance is called change'. 

 

Types of Changes

Types of changes on the basis of either the changes can be reversed to bring back the original substance or not:

 

Reversible Change

A change which can be reversed to form the 'original substance' is called reversible change. For example, melting of ice, freezing of water, dissolution of salt in water, increase in temperature of a metal rod, etc.

 

Irreversible Changes

A change which cannot be reversed to form the 'original substance' called irreversible change. For example, burning of wood, ripening of fruit, turning milk sour, etc.

Types of changes on the basis of either a new substance is formed or not:

 

Physical Change

The change, in which molecules of a substance do not undergo any change or no new substances are formed, are called physical changes. For example, melting of ice, freezing of water, evaporation of water, dissolution of salt in water.

 

Chemical Change

The change, in which molecules of substance undergo change or new substances are formed, are called chemical changes. For example, burning of paper, rusting of spoliation of food, etc.

Types of changes on the basis of heat absorbed or evolved:

 

Exothermic

The change in which heat is released. For example, burning of wood.

 

Endothermic

The change in which heat is absorbed. For example, melting of ice.


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