Final answer:
Liquids and gases can flow due to their particle arrangement, whereas solids cannot due to strong intermolecular forces. Gases can be compressed as there is substantial space between particles, but solids and liquids cannot due to close particle packing.
Step-by-step explanation:
Liquids and gases are both considered fluids, as they can flow and be poured, a property that stems from the movement, spacing, and arrangement of their particles, and the intermolecular forces between them. In contrast, solids cannot flow, which is due to the fixed positions of their particles and the strong intermolecular forces that hold these particles in a rigid structure. Gases are easily compressed because there is a lot of space and relatively weak forces between the particles, which are spread out and move freely to fill their container. While solids have a definite shape and volume and are not compressible due to the lack of space between closely-packed particles, liquids are not compressible for a similar reason, even though they can take the shape of their container. This unyielding nature is attributed to the nearby presence of other particles, even though they are not fixed in place, allowing the liquid to adapt to the shape of its container without a significant change in volume.