It may be somewhat surprising to learn that there is no fundamental distinction between a gas and a liquid. It was noted above that a gas occupies a volume about 1,600 times greater than that of an equal weight of liquid. The question arises as to the behaviour of a gas that has been compressed to 1/1,600 of its volume by application of sufficiently high pressure. If this compression is carried out above a specific temperature called the critical temperature, which is different for each gas, no phase change occurs, and the resulting substance is a gas that is just ...(100 of 12577 words)