* Solids: Solids have a fixed volume and shape. Their particles are tightly packed and vibrate in fixed positions.
* Liquids: Liquids have a fixed volume but take the shape of their container. Their particles are close together but can move around.
* Gases: Gases have neither a fixed volume nor a fixed shape. Their particles are far apart and move freely.
Therefore, only solids have a fixed volume. Liquids and gases can change their volume depending on the conditions (pressure and temperature).
