Final answer:
The state of matter that spreads and fills the entire available space is Gas. Solids maintain a defined shape, liquids take the form of their container but maintain a fixed volume while gases take both the volume and the shape of their container. Matter sometimes can exhibit properties of more than one state.
Step-by-step explanation:
In the context of the three states of matter; Solid, Liquid, and Gas, the state in which matter spreads and fills the entire available space is Gas.
Solids and Liquids have volumes that are nearly independent of pressure unlike Gases. Solids maintain a certain rigid shape, whereas liquids take the form of their container but form a flat or curved surface at the top. On the other hand, Gases take both the volume and the shape of the container.
However, it's important to mention that in certain conditions, matter can exhibit properties of more than one state. For instance, clouds appear to behave somewhat like gases but they are mixtures of air (gas) and tiny particles of water (liquid or solid).
Learn more about States of Matter