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States of Matter


Matter can be classified into three categories depending upon its physical state, namely: solids, liquids and gases. These states of matter arise due to variation in the characteristics of the particles of matter. 


(i) The matter in solid state possesses a definite volume, a definite shape, distinct boundaries and a definite mass.

(ii) Solids are rigid and almost incompressible.

(iii) Solids may break under force but it is difficult to change their shape.

(iv) Solids generally possess high densities.

(v) Solids do not exhibit diffusion. Some common examples are: table, chair, common salt, silver, ice, diamond, etc.



(i) The matter in liquid state possesses a definite volume, a definite mass, but no definite shape.

(ii) Liquids are also almost incompressible but are not rigid. In fact, they can flow and acquire the shape of the container in which they are kept.

(iii) Liquids can undergo diffusion.

(iv) Liquids also have high densities but less than that of solids.

Some examples are: milk, water, alcohol, petrol, kerosene, fruit juices, etc.



(i) The matter in gaseous state has neither definite volume nor definite shape but it has definite mass. It acquires the shape and volume of the container.

(ii) Gases are highly compressible. For example, natural gas in compressed form is used as fuel (Compressed Natural Gas-CNG) in internal combustion engines. Oxygen supplied to hospitals in cylinders is also in compressed form. Due to high compressibility large volumes of gas can be compressed into a small cylinder and transported easily.

(iii) The gases exhibit the property of diffusing very fast into other gases.

(iv) Gases exert pressure on the walls of the container in which they are stored.

(v) Gases have very low densities.

Some common examples of gases are: air, hydrogen  carbon(IV) oxide, hydrogen, sulphide, ammonia, oxygen, nitrogen, etc.

A comparison of the characteristic properties of solids,  liquids and gases are given in Table 4.1.


Table 4.1. Comparison of Characteristic Properties of Solids, Liquids and Gases

Property                      Solids                          Liquids                        Gases

l.Sbape                        Definite                       Take the shape           Take the shape of

of the con                    the container by

tainer, but do               occupying whole

not necessarily             of the space avaoccupy

all of it.                        ilable to them.


2. Volume                   Definite                      Definite                      Take the volume

of the container.


3. Compre-                  Almost            nil                   Almost nil                   Very large.



4. Fluidity or               Rigid                           Fluid                                        Fluid



5. Density                    Large                           Large                           Very small.


6. Diffusion                 Generally                    Diffuse slowly            Diffuse rapidly.

do not



7. Free                         Any                             Only one free              No free surface.

Surfaces                      number of                               surface




Why Solids, Liquids and Gases Exhibit Different Properties?

The properties of matter in the three states of matter are different because the characteristics of the particles vary in the three states of matter.

Now let us understand how the characteristics of particles vary in the three states of matter.

  • In solids, the interparticle spaces are small. They have smaller amounts of energy than the same particles in the liquid and gaseous states. Consequently, the particles in solid state cannot overcome the strong forces of attraction which are holding them together. In solids, particles can only vibrate about fixed positions. Thus, particles in a solid have vibrational and rotational motion but no translational motion. Because of smaller interparticle spaces, solids are almost incompressible while due to absence of translational motion they are rigid.
  • In liquids, interparticle spaces are somewhat larger than in solids and the particles have larger amounts of energy. The particles in liquids can overcome the interparticle forces between each other to some extent and hence can move freely. However, the intermolecular forces in liquids are strong enough to keep the particles within the bulk. The particles in liquid state possess vibrational, rotational and translational motion.

Fig. 4.2. Different types of motion.

  • In gases, the interparticle spaces are very large and the particle possess much larger amounts of energy than those in solids and liquids. The gas particles have sufficient energy to overcome the interparticle attractive forces almost completely. As a result the gas particles move rapidly and randomly into any space available to them. Thus, a gas fills completely the vessel in which it is kept. That is why gases have neither definite shape nor definite volume. Since particles in gaseous state are free to move, they collide with one another and also against walls of the container. The pressure of the gas is due to collisions of molecules against walls of the container.


Fig. 4.3. Packing of particles in  the three states of matter.

  • Solid and liquid states are known as condensed states of matter due to smaller interparticle spaces” and negligible compressibility.
  • Liquids and gases are known as fluids because of their ability to flow and take the shape of container


PLASMA STATE-The Fourth State of matter

The matter in this state is in the form of ionized gas. It consists of neutral mixture of positive ions and unbound electrons. The matter exists in this state at temperatures in the range 10000°C to 15000°C. The matter in the sun and stars exists in plasma state. It is estimated that 99% of the matter in the universe exists in plasma state. Neon in neon lights is also in plasma state

  • Matter is anything that occupies space and has mass.
  • Matter can be classified as solids, liquids and gases on the basis of its physical state.
  • Matter is made up of extremely small particles.
  • There are spaces between particles of matter.
  • The particles of matter are continuously moving.
  • The particles of matter attract each other.
  • The spaces between particles are minimum in solid state and maximum in gases.
  • The kinetic energy of particles minimum in solid state and maximum in gaseous state.
  • The force of attraction between particles is maximum in solid state and negligible in gaseous state.
  • Liquids and gases exhibit diffusion because their particles possess translatory motion and possess larger interparticle spaces.
  • Solid and liquid states are known as condensed states of matter due to smaller interparticle spaces and very little compressibility.
  • Liquids and gases are known as fluids because of their ability to flow and take the shape of the container.



I. Objective Type Questions

Select the most appropriate choice from the options given as (a), (b), (c) and (d) after each question:

1.Which of the following is not an example of matter?

(a) Air                          (b) Almonds

(c) Cold-drink             (d) Love.


2. Which of the following has the strongest interparticle forces?

(a) Nitrogen                 (b) Water

(c) Iron                        d) Neon.


3 Which of the following has atoms as the constituent particles?

(a) Dry ice                   (b) Argon

(c) Glucose                  (d) Potassium chloride.


Fill in the blanks

Complete the following sentences by supplying appropriate words:

(i) The particles in …… state do not possess translator motion.

(ii) …… and …… states of matter are known as fluid states of matter.

(iii) Particles in …… state possess maximum kinetic energy.

(iv) Kinetic energy of particles of matter …… with increase in temperature.


I .Discussion Question 

5 What are the characteristics of the particles of matter?

6. Which out of iron and chalk has stronger interparticle forces?

7. Give reasons for the following observations:

We can get the smell of perfume sitting from several meters away.

8. A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

9. Describe an activity to demonstrate that the matter consists of particles and that the particles are of extremely small size.

10. What are the characteristics of matter in solid state?

11.P Explain why:

(i) Solids do not undergo diffusion whereas liquids and gases undergo diffusion readily.

(ii) Gases are highly compressible.

12. Give reasons for the following:

(i) A gas fills completely the vessel in which it is kept.

(ii) A gas exerts pressure on the walls of the container.

11. Explain why solid and liquid states are known as condensed states of matter.

14. Give reasons:

(i) Sponge is a solid yet we are able to compress it.

(ii) Sugar when kept in jars of different shapes it takes the shape of the jar yet we call it a solid.