- Books Name
- CBSE Class 6 Science Book
- Param Publication
- CBSE Class 6
(ii) Periodic and non-periodic changes
(a) Periodic change : 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.
(b) Non periodic change : 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.
(iii) Desirable and undesirable changes
(a) Desirable change : Some changes are beneficial for the mankind and we desire them to happen. Such changes are called desirable changes.
eg. ripening of fruits, photosynthesis
(b) Undesirable change : Some changes are harmful for us, and we need to stop them. Such changes are called undesirable changes.
eg. Spoilage of food, rusting of iron.
(iv) Natural and Man-Made changes
(a) Natural change : A change that occurs naturally on its own is called a natural change.
eg. changing of season, occurence of tides, eclipses.
(b) Man-made change : A man-made change is the one that occurs because of human activities.
e.g. Changing the direction of flow of a river by building a dam.
(v) Slow and Fast changes
(a) Slow changes : Some changes take place at a slow rate, such changes are called slow changes.
eg. Growth of plant, rusting of iron
(b) Fast changes : Some change take place in a fraction of second, such changes are called fast changes
eg. Occurence of lightning during thunderstorm, earthquakes.