NATURE OF MATTER - Anything that occupies space and has mass is known as matter. Everything around us is a form of matter. The huge buildings, bridges, electrons  revolving around a nucleus, the DNA in our cells, the air around us, the land beneath our feet, etc. all matter. A matter is said to be composed of particles which are basically atoms and molecules. Depending upon its physical state, the nature of matter falls into three categories:

1. Solids:
3. The substances in which the particles are held close to each other with strong intermolecular forces are known as solids. The particles are strongly held at their positions and have only vibratory motion. Solids have a definite shape and definite volume. E.g.: Wood, iron etc.
5. Liquids:
7. Those substances in which the intermolecular forces are weak enough to allow the movement of particles are known as liquids. The particles are held closely and have a higher degree of freedom than solids. Liquids have a definite volume but no definite shape; they generally take the shape of the container in which they are placed. E.g.: water, milk, etc.

1. Gases:
3. These types of matter have very weak forces between their molecules and hence the molecules are free to move. The distance between molecules is large as compared to solids and liquids. Gases have neither fixed shape nor a definite volume. They tend to completely occupy the container in which they are placed. E.g. air, oxygen (https://byjus.com/chemistry/oxygen/) , hydrogen, methane, etc.

The above three states of matter can be transformed from one form to the other by changing the conditions of temperature and pressure. The nature of matter is also determined by its composition. If the matter is composed of more than one type of particles then it is called as a mixture while if it consists of a single type of particles then it is known as a pure substance. Mixtures are further classified as homogeneous and heterogeneous mixtures. Pure substances are also sub-divided as elements and compounds.