Solid, Liquid and Gases
In a solid, the particles fit very closely together. They are repeatedly vibrating and twisting but they do not move past their neighbor particles because the particles are very close to each other. They attract their neighboring particles. This is why solids keep their own shape and to stay where they are put. They are very difficult to compress. They have very small gaps in between the particles.
In a liquid, the particles are still close together but a little further apart in comparison to a solid. The particles can move around and mix with other particles. Therefore, liquids can change shape to according to their container. There is still very little space between particles so liquids are difficult to compress.
In gases, the particles are much further apart in comparison to both solids and liquids. There is a lot of space in between the particles and they keep moving about. The particles collide with other particles and with the walls of the container. Because the particles can move easily, a gas will fill any container that is put into. There is space between the particles. They can be compressed into a smaller volume when the gas is compressed.