Changes Around Us

Change :- Any difference in the size or shape of an object is referred to as a change. Many changes are taking place around us on their own. In the fields, the crops change from time to time. Sometimes, leaves fall from trees, change colour and dry out.

The flowers bloom and then wither away. We also find that some changes can be reversed, while some others cannot be reversed. Thus, changes around us could be grouped as those that can be reversed or cannot be reversed.

Reversible Change:-

There is a change in the physical properties, shape and size of the material. Mostly a new substance is not formed in a reversible change. For example, folding of paper, boiling water, breaking a glass, melting an ice cube, freezing water etc.

Irreversible Change:- The change, which is permanent and cannot be undone by any physical or chemical means, is called an irreversible change. The formation of new substances is involved in this change. For example:- Burning wood, Souring milk, Mixing acid and a base, Digesting food, rusting iron etc.

Expansion:- When the temperature increases, the particle of a substance expands or becomes loose. It is known as Expansion.

Contraction:- When the temperature decreases, the particles of the substance contract or become tight.