Matter

—Any collection of substance existing by itself in a separate form; matter appears in various forms which, however, can all be reduced to three cla es; namely, solids, liquids, gases; a solid offers resistance to change of shape; it has a fixed form and is hard, firm and compact. A liquid is a substance which flows and can be poured in drops, like water. A liquid flows, and wets that on which it flows. A gas is a fluid form of matter which is elastic and tends to expand indefinitely. A term used at first by chemists as synonymous with air, but since restricted to fluids supposed to be permanently elastic; as, oxygen, hydrogen, etc., in distinction from vapors, as steam, which become liquid on a reduction of temperature.: The two e ential properties of matter, both of which are inseparable from it, are extension and impenetrability. Extension, in the three dimensions of length, breadth and thickne , belongs to matter under all circumstances; and impenetrability, or the property of excluding all other matter from the space which it occupies, appertains alike to the largest body and the smallest particle.