INTRODUCTION

Physically matter is classified into three states i.e. solid, liquid, gas. But, matter can't be distinguished just by their physical properties like density, mobility, viscosity, etc. Solids at ordinary conditions have definite volume and shape and tend to maintain these even under deforming forces ( i.e. external forces that tend to change its initial shape ). Liquids also have a definite volume but take the shape of the vessel/container they are kept in. Both solids and liquids are equally nearly incompressible gases; do not maintain fixed volume and shape. It completely fills the container in which it is kept. Gases can be expanded and compressed very easily.

The three states of matter are interconvertible i.e. they can be changed into one another by heating or cooling. Heat energy increases the inter-molecular distance and kinetic energy of the molecules. So, solids are converted to liquids on heating and liquids are converted to gas.

The effect of heat on the particle of solid, liquid and gas is shown as-