and the name o the most important one and the evidence for this?
All matter is made from atoms. In the solid phase the molecules are closely bound to one another by molecular forces. A solid holds its shape and the volume of a solid is fixed by the shape of the solid. In the liquid phase the molecular forces are weaker than in a solid. A liquid will take the shape of its container with a free surface in a gravitational field. In microgravity, a liquid forms a ball inside a free surface. Regardless of gravity, a liquid has a fixed volume.
In the gas phase the molecular forces are very weak. A gas fills its container, taking both the shape and the volume of the container.
Defenitions from: http://funadvice.com/r/14pasrrm0ib
They are all very important, there all beneficial in a way. Everything around us is evidence for this. The petrol we put into our cars is a example of gas. The water we consume everyday is a liquid. The tables and chairs we use everyday are solids.