1. Kinetic Theory of matter
According to the kinetic theory,
All matters are made up of a large number of tiny particles.
All the particles are vibrating or moving randomly(always change direction).
Temperature of an object is related to the average K.E. of its particles.
T   particles vibrate more rapidly (in solid) or move faster(in liquid and gas)
T   particles slow down

2. Kinetic Theory & different states
Kinetic Theory explains the differences between the three states of matter.
liquid
solid
gas
In gases, the particles have enough kinetic energy to break all intermolecular forces of attraction.
In solids, the particles have low kinetic energy and they are held together by intermolecular forces of attraction.
In liquids, the particles have more kinetic energy to stretch the intermolecular forces of attraction.

3. Kinetic Theory of Gas
The kinetic theory of gas describes a gas as a large number of small particles. They are moving in random direction.
The rapidly moving particles constantly collide with each other and with the walls of the container.
Kinetic theory explains the properties of gases, such as pressure, temperature and volume.