Here's why:
* Solids have tightly packed particles that are held together by strong forces. This arrangement gives them their rigid structure, meaning they maintain their shape.
* Liquids have particles that are closer together than gases, but they can move around each other more freely. They take the shape of their container but have a definite volume.
* Gases have particles that are spread far apart and move freely. They take the shape and volume of their container.
