The main reason why we learn about the different states of matter is to be able to relate to the physical world. The matter is defined as anything that occupies space and has a mass. There are three major states of matter which include solid, liquid, and gas.
A substance is solid if at atmospheric pressure its melting point is well above the room temperature of 25 degrees Celsius. The physical properties of a solid are due to the strong forces of attraction. Other characteristics of solid include definite shape, diffuse slowly, and it cannot be compressed except under high pressure.
A substance is liquid if at atmospheric pressure it melts at room temperature below room temperature of 25 degrees Celsius and boils at a temperature above room temperature. The physical properties of a liquid are because the forces of attraction between the particles are not strong.
A substance is a gas if at atmospheric pressure it boils at a temperature below the room temperature. The physical properties of a gas are because the particles are held together by extremely weak Van der Waals forces.