Anything, that has a mass and occupies space, is
The common states of matter are solid, liquid and
gas. Gases have neither definite shape nor volume,
liquid has definite volume but no definite shape,
whereas solid has definite shape as well as definite
Liquid takes the shape of vessel in which it is
kept, but does not occupy total volume available,
whereas gas takes the shape of vessel as well as
occupies all the space available to it.
According to kinetic molecular theory, matter is
composed of particles, which are called molecules.
Molecules are in motion and they possess kinetic
The three states of matter depend upon arrangement,
motion and forces of attraction between their
In solids molecules are tightly packed with one
another and they perform only translational motion.
Due to this, molecules in solid neither slip nor
slide over one another, hence shape and volume of
solid is definite.
Interconversion of three states of mate are common
and they may be seen by us, just like change of ice
to water, evaporation of water and sublimation of
iodine, ammonium chloride and napthaline.
During melting, solids are converted into liquids
and in this process movement of particles overcome
the intermolecular attractive forces.
Certain solids are directly converted into gaseous
state during heating and this process is called
In gaseous state, molecules are widely separated
from one another and they move freely in all
direction; hence the shape and volume of gas are not
When vapour pressure of a liquid becomes equal to
external pressure, then it starts boiling and the
temperature is called the boiling point. During
boiling bubbles of vapours are able to form within
the bulk of liquid and then rise to the surface,
where they burst and release vapours. In other
.words in this way liquid is converted into gas.
At boiling point the temperature of liquid remains
same until all of the liquid is vapourized to gas.
This change is called as vapourization or