​CHANGE

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

• ​ Changes are either reversible or irreversible .

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​TYPES OF CHANGES

• ​periodic and non-periodic change

• ​Expansion and contraction

• ​slow and fast change

• ​desirable and undesirable change

• ​natural and man made change

• ​physical and chemical change

• ​reversible and irreversible change

SLOW CHANGE- ​The changes happening over a long period of time are considered as slow changes. Example: Rusting of iron.

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​FAST CHANGE- The changes that occur within a short time frame are considered as fast changes. Example: Crackers burst.

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​PERIODIC CHANGE - Changes that repeat at regular intervals are called periodic changes.

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​NON PERIODIC CHANGE - Certain changes that do not repeat themselves at regular intervals of time, and such changes are called non-periodic changes.

​Expansion and contraction Substances expand (increase in size) when they get warmer, and they contract (decrease in size) when they get cooler. This property can be useful.

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​Desirable changes are those changes which we want to occur. These changes are useful to us. For example ripening of fruits, germination of seeds, change in season. Undesirable changes are those changes which we do not want to take place are called undesirable changes.

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​The change that occurs natural on its own is called natural change. A man-made change is the one that occurs because of human activities.

​A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.

• Examples of chemical changes are burning, cooking, rusting, and rotting.

• Examples of physical changes are boiling, melting, freezing, and shredding.

• Many physical changes are reversible, if sufficient energy is supplied. ...

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​The changes which can be brought back to their original form are known as reversible changes. For example, melting of ice, expansion, or compression of spring. And irreversible changes are those changes in which the matter cannot be brought back to its original state. For example, burning of fuel, etc.

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