Page 54 - Science Class 06
P. 54
Liquids The given three states of ma er can be
Those substances in which the inter- transformed from one form into the other
molecular forces are weak enough to allow by changing the condi ons of temperature
the movement of par cles are known as and pressure. The nature of ma er is also
liquids. The par cles are held closely and determined by its composi on. If the ma er
have a higher degree of freedom than is composed of more than one type of
solids. Liquids have a definite volume, but par cles, then it is called as a mixture while
if it consists of a single type of par cles,
no definite shape; they generally take the
shape of the container in which they are then it is known as a pure substance.
placed, e.g., water, milk, etc. Mixtures are further classified as homogen-
eous and heterogeneous mixtures. Pure
substances are also sub-divided as elements
and compounds.
The states of ma er are interchangeable
Most of the forms of ma er can change
from one state to another and also reserve
back to their original forms. Water is a
common example that explains this feature
of ma er. Water, as a solid, is ice.
Liquid
Gases v When ice melts due to heat, it becomes
a liquid— water.
These types of ma ers have very weak
intermolecular forces between their v When water is put on fire, it changes
molecules and hence the molecules are free into vapour which is a gas.
to move. The distance between molecules is In the reverse process—
large as compared to solids and liquids. v Vapour, on touching a cold surface,
Gases have neither fixed shape nor a definite changes back to liquid form – water.
volume. They tend to completely occupy the
v This liquid (water) when placed in a
container in which they are placed, e.g., air,
refrigerator, freezes into ice.
oxygen, hydrogen, methane, etc.
MATTER IS PARTICULATE
We have learnt the following important
facts about ma er:
v Materials are various forms of ma er.
v Ma er is concrete, has mass and
occupies space.
v Ma er has three states—solids, liquids
and gaseous.
Gas v These three states are interchangeable.
54 Science-6
