Wiccan views of divinity the ancient Greek conception, where the elements correspond to matter (earth) and energy (fire), with the mediating elements (water, air) relating to the phases of matter (fire/earth mixtures). A more modern conception correlates the four elements to the four states of matter known to science: Solid (earth); Liquid (water); Gas (air); and Plasma (fire); with the akasha element corresponding to pure Energy. The Aristotelian system proposes a fifth or quintessential element, spirit (aether, akasha). The preferred version is a matter of ongoing dispute in the Wiccan community. There are other non-scientific conceptions, but they are not widely used among Wiccans.
State of matter below its critical temperature, a gas is also called a vapor, and can be liquefied by compression alone without cooling. A vapor can exist in equilibrium with a liquid (or solid), in which case the gas pressure equals the vapor pressure of the liquid (or solid). A supercritical fluid (SCF) is a gas whose temperature and pressure are above the critical temperature and critical pressure respectively. In this state, the distinction between liquid and gas disappears. A supercritical fluid has the physical properties of a gas, but its high density confers solvent properties in some cases, which leads to useful