* Solids: Have a fixed shape. Their particles are tightly packed and arranged in a regular, rigid structure. They maintain their shape even when moved or placed in a different container. Think of a rock, a piece of metal, or a block of ice.
* Liquids: Take the shape of their container. Their particles are closer together than gas particles, but they can move around freely. They flow and adjust to the shape of their container, but they have a definite volume. Imagine water in a glass, bottle, or puddle.
* Gases: Have no fixed shape and fill their container. Their particles are spread far apart and move randomly. They take the shape and volume of whatever container they are in. Think of air in a balloon, room, or tire.
In a nutshell:
* Solids: Fixed shape, fixed volume.
* Liquids: No fixed shape, fixed volume.
* Gases: No fixed shape, no fixed volume.
