Question

a) State kinetic theory of matter.
(b) Differentiate the three states of matter in
terms of movement of particles.
3. On the basis of kinetic theory of matter explain
(a) Why the solids have a definite volume and
definite shape?
(b) Why the liquids have a definite volume, but
no definite shape?
4. (a) Describe energy content in the three states
of matter
(b) Describe the change of state using kinetic
theory..​

Answer 1

Explanation:

KINETIC THEORY OF MATTER

The theory which reveals that any substance whether solid, liquid or gas is made up of tiny particles called atoms, molecules or ions which are in constant motion is called "kinetic theory of mater". The main postulates of this theory are :

• Matter is composed of very small particles called atoms and molecules.

1. The constituent particles of a kind of matter are identical in all respects.
2. These particles have spaces or gaps between them which are known as interparticular or intermolecular spaces.
3. There exists a force of attraction between the particles of matter which holds them together. This force of attraction is known as
4. Particles of matter are always in a state of random motion and possess kinetic energy, which increases with an increase and vice-versa. in temperature.

EXPLANATION OF STATES OF MATTER BASED ON KINETIC THEORY

Solid state : In solids, the particles (molecules) are closely packed. There is a strong force of attraction between the particles (molecules) and the intermolecular space is almost negligible. The molecules are therefore, not free to move. They only vibrate about their mean positions. This makes solids hard and rigid and difficult to compress, giving them a fixed shape and size, Solids have low kinetic energy.

Liquid state : In case of liquids, the particles are not very closely packed. The intermolecular forces of attraction are not as strong as in the case of solids, thus the intermolecular. energy. spaces are larger. The molecules are loosely packed, hence liquids-are more compressible. The particles are able to move freely and randomly. The kinetic energy is higher than that of solids. This makes a liquid flow and take the shape of the container into which it is poured. Thus, liquids have a fixed volume but no definite shape.

Gaseous state : In case of gases, the intermolecular forces of attraction are negligible. The particles lie far apart from each other and the intermolecular spaces are therefore, very large. Hence they can be compressed. The forces of attraction are so weak that the particles of gases are free to move within the entire space availble to them. They have high kinetic energy. During motion, these particles collide with each other and also with the walls of the container.As a result, gases have neither a fixed shape nor a fixed volume. They completely fill up the space available to them.