Question

Differentiate between the following, giving at least one point of difference.
(a) periodic and non-periodic changes
(b) irreversible and reversible changes
(c) vaporisation and sublimation
(d) physical and chemical changes
(e) evaporation and boiling

Answer 1

(a)

Periodic changes	Non-periodic changes
They are cyclic changes that occur at regular intervals of time and have a fixed pattern.	They do not have a fixed pattern and do not occur at fixed intervals of time.
Example: Seasons	Example: Souring of milk

(b)

Irreversible changes	Reversible changes
The changes which can not be reverted back are called irreversible change.	The changes which can be reverted back are reversible changes.
Example: Photosynthesis	Example: Melting of ice

(c)

Vaporisation	Sublimation
The conversion of liquid into vapours is called vaporisation.	The conversion of solid into gas is called sublimation.

(d)

Physical changes	Chemical changes
The changes that do not involve a change in the properties and identity of a substance are called physical changes.	The changes that involve changes in the properties of a substance or formation of a new substance is called chemical change.

(e)

Evaporation	Boiling
It is a slow process.	It is a faster process.
Bubbles are not formed.	Bubbles are formed.