Final answer:
Solids have closely packed molecules, resulting in a definite shape and volume. They are not easily compressed due to strong intermolecular forces and do not take the shape of their containers unlike liquids or gases.
Step-by-step explanation:
Solids are materials where the molecules or atoms are closely packed together, resulting in a substance that has a definite shape and volume. Unlike gases, which can fill their containers, or liquids, which can adapt the shape of their containers, solids maintain their shape and do not conform to the space they are placed in. This rigidity is due to the strong intermolecular forces that keep the particles in fixed positions. Additionally, because of the lack of space between molecules, solids are not easily compressible and have high densities. The particles in a solid may vibrate around fixed positions but do not have enough kinetic energy to move freely past each other, distinguishing them from the behaviors found in liquids and gases.