Question

Distinguish between the following.
(a) Physical change and chemical change
(b) Periodic change and non-periodic change
(c) Natural change and man-made change

Answer 1

a.

Physical Change	Chemical Change
The chemical composition of a substance does not change	The chemical composition of a substance does not remain same
Easily reversible	Not easily reversible
No new substance is formed	New substances are always formed
Melting of ice is an example of physical change	Burning of paper is an example of chemical change

b.

Periodic changes	Non periodic changes
1. Events that repeat themselves after a fixed period of time and whose ocurence can be predicted are called periodic changes.	The events that do not repeat themselves after regular interval of time are called non periodic changes.
2. Example- rotation of earth, revolution of earth, day and night, seasons etc.	Example- natural disasters like earthquake, cyclones etc.

c.

Natural changes	Man made changes
1. The changes which are brought about by nature itselfand are not under the control of humans are called natural changes.	The changes which are brought about by humans are called man made changes.
2. Examples- change of season, tides in sea, ageing of plants etc.	Examples- burning of fuels, cutting hair, switching on lights etc.