What state of matter has no definite shape or volume?

The state of matter characterized by having no definite shape or volume is gas. In this state, the particles are in constant motion and are far apart from each other compared to solids and liquids. Because of this separation, gases can expand to fill their containers, taking both the shape and volume of that container.

In gases, the intermolecular forces are very weak, allowing the particles to move freely and quickly. This results in a lack of a fixed shape; gases will uniformly occupy any available space. Additionally, they can be compressed significantly, further reinforcing the notion that they do not have a definitive volume.

While solids have a definite shape and volume due to closely packed particles that vibrate in place, and liquids have a definite volume but no fixed shape—they take on the shape of their container—gases exhibit neither of these properties, making them unique among the states of matter. Plasma, although similar to gas in lacking a definite shape and volume, consists of ionized particles and is often found at very high temperatures, such as in stars, but is not a common state observed at standard conditions on Earth.