Final answer:
The three states of matter are determined by the arrangement and movement of atoms and their kinetic energy. Solids are closely packed and vibrate in place; liquids are less tightly packed and able to slide past one another; gasses are spread out with free-moving particles that fill their container.
Step-by-step explanation:
The cause of three different states of matter is fundamentally tied to the behavior of molecules, atoms, their arrangement, movement, and kinetic energy. In a solid, atoms are in close contact and are arranged in a fixed, closely packed structure that only allows them to vibrate but not to move freely. The kinetic energy in solids is low because the temperatures are relatively low so that the atoms do not have enough energy to overcome the intermolecular forces that hold them together.
In a liquid, atoms or molecules are still in close contact but have more kinetic energy compared to solids. This energy allows them to move and slide past each other, thus enabling a liquid to take the shape of its container while maintaining a fixed volume. The particles are less closely packed than in a solid, making liquids less rigid.
In the case of a gas, the molecules have sufficient kinetic energy to overcome intermolecular forces significantly, leading them to be spread out. This high level of energy results in particles that move rapidly and independently of one another, allowing a gas to expand to fill the entirety of its container, and it assumes both the shape and volume of its container.