Study Material

Change is a permanent part of our lives. A change could alter physical properties or chemical properties or both of the concerned matter. These changes may be observe by us at school, at home, in the playground in the garden or any other place. A change can bring about different kinds of effect in the things around us. Some of the effect brought about are permanent in nature, and hence, cannot be reversed . However, some effects are about in position, shape, size or state of the things. These effects are temporary in nature, and hence can be reversed. 

 

 

A change which can be reversed by the conditions is called a reversible change. 

Eg. Melting of ice, dissolving of salt in water 

A change that cannot be reversed by reversing the condition is called an irreversible change. 

    Eg. Burning of paper, curdling of milk 

 

 

A change which is repeated after regular intervals of time is called a periodic change. Swinging of a pendulum, rising and setting of the sun at a given place, and change of seasons are some examples of periodic changes. A changes which does not occur after regular intervals of time is called a non-periodic change. Most of the changes happening around us are non-periodic changes, occurrence of floods and cyclones are some of them.

 

 

A change that occurs naturally on its own is called a natural change. Eg. changing of season, occurence of tides, eclipses. A man-made change is the one that occurs because of human activities. 

e.g. Changing the direction of flow of river by building a dam. 

 

 

 

Some changes take place at a slow rate, such changes are called slow changes. 

Eg. Growh of plant, rusting of iron Some change take place in a fraction of second, such changes are called fast changes 

Eg. Occurance of lightning during thunderstrom, earthquakes.

 

 

(1) Some objects simply get hot, but no other changes take place. 

When you drink hot milk or coffee from a cup. you may feel that the cup however no change in the state of the cup take place. 

 

(2) Some object get hot and expand. 

Eg. Metal key on heating got hot as well as increased in size. 

 

(3) Some object get hot and expand. 

Eg. The candle is lighted it starts burning. Its shape and size also changed. 

 

(4) Some of the change their state. 

Eg. Ice is heated it change
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