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Changes in nature
In the day-to-day life, so many changes are taking place across many things around us. For example, day turns to night, growing crops in the agricultural field, falling leaves from trees, blooming of flowers, etc.
Changes in the human body
Example:
The growth of nails, hair, ageing, increasing height and weight.
What is change?
Change is a process in which a substance becomes a different one from what it was earlier. It is the difference between the initial and the final state of any substance.
The difference in the size or shape of an object is termed as a 'change'. Change can be either reversible or irreversible. The changes around us can be generally classified into two main types, namely, reversible change and irreversible change.
Reversible change
The changes that can be reversed to form its original shape and size is termed as reversible change.
Example:
Freezing of water, melting of ice, stretching of a rubber band, inflation of a balloon, and folding of paper.
1. A balloon is blown-in such a way that it does not burst. There is a change in the shape and size of the balloon on blowing air into it. Now, when the air is made to escape out of the balloon, again it turns to its original shape and size.
2. A toy ship is made by folding a sheet of paper. When we unfold the paper again, it comes to its original shape as before.
3. Likewise, a dough is made into a ball and rolled it out into a roti. If its shape is not good, it can be changed back into a ball of dough.
In all the above examples, the substances are changed into its original shape and size.
Physical change
In the physical change, only the physical properties such as colour and size are changed. No new substances are formed in this type, and they can be reversible. For example, the spring may not come to its original size as before, and when a paper is unfolded, it may have the marks of its folding.
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