# Three States of Matter: Solid, Liquid and Gas

### What is Matter?

Materials which we see in our daily lives such as ice-cream, chair, water etc. are made up of the matter. Matter can be classified as solid, liquid and gas on the basis of inter-molecular forces and the arrangement of particles. These three forms of matter can be converted from one state of matter to another state by increasing or decreasing pressure and temperature. For example, Ice can be converted from solid state to liquid state by increasing the temperature.

Change in state of matter alters the structure of matter and the arrangement of particles. All this can be observed by noticing the change in properties.

### The Three States of Matter:

Description of various states of matter:

1. #### Solid state:

The Solid state is one of the fundamental states of matter. Solids differ from liquids and gases by the characteristic of rigidity. The molecules of solids are tightly packed because of strong intermolecular forces; they only oscillate about their mean positions. Whereas, liquids and gases possess the property of fluidity and can easily flow. Solids can be defined as the state of matter which has definite shape and volume and has a rigid structure. Solids possess the least compressibility and thermal expansion.
Example: Iron (Fe)

2. #### Liquid state:

The molecules in a liquid are closely packed due to weak intermolecular forces. These forces are weaker than solids but stronger than that of gases. There is much space in between the molecules of liquids which makes their flowing ability easy. Liquids can easily acquire the shape of a vessel and they have a fixed volume.Conversion of solids into liquids takes place when we increase the temperature of solids to a point where solids begin to melt. Generally, the density of liquid lies between the density of solids and gases. Compressibility and thermal expansion of liquids are slightly higher than that of solids.
Example: Water (H2O)

3. #### Gaseous state:

In this state of matter, distances between the molecules are large (intermolecular distance is in the range of $10^{-7} – 10^{-5} cm$)). The intermolecular forces experienced between them are negligible. Thus translatory, rotatory and vibratory motions are observed prominently in gases. Gases do not have any fixed shape or volume. They also possess high compressibility and thermal expansion.
Example: Oxygen (O2)