Kinetic Molecular Theory
The molecular theory of matter assumes that matter is made up of atoms that add up to molecules.
The atom is the smallest particle of an element that can have a separate existence and still retain the chemical properties of the element.
A molecule is a group of atoms of the same or different elements joined together in a simple proportion.
The molecules in solids are in fixed positions and vibrate about their mean position. Solids have definite shapes and volumes due to intermolecular forces of attraction and repulsion existing between the molecules.
The molecules are freer to move about within the liquids than in the solids. The intermolecular forces of attraction existing between the molecules are weaker compared to that of the solid, hence they can move about unlike that of solid.
The molecules are in constant motion having overcome the intermolecular forces of attraction existing between them. They have no definite shape and volume but only take up the shape of the container. The molecules are farther apart than those of solids and liquids and have the highest energy compared to solids and liquids.
This is the state in which the sun’s rays reach down to the earth. It is a state of completely free-charged particles found at extremely very high temperatures.