Liquid a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, and much higher than in a gas. Therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, they are both called fluids. Although liquid water is abundant on Earth,
Hidden states of matter exists in equilibrium, but is not immediately apparent or easily observed. Using ultrashort laser pulses impinging on solid state matter, the system may be knocked out of equilibrium so that not only are the individual subsystems out of equilibrium with each other but also internally. Under such conditions, new states of matter may be created which are not otherwise reachable under equilibrium, ergodic system evolution. Such states are usually unstable and decay very rapidly, typically in nanoseconds or less. The difficulty is in distinguishing a genuine hidden state from one which is simply out of thermal equilibrium. Probably the first