Solids
Matter exists in three forms--solid, liquid, and gaseous. When the particles of a body cohere, as in ice, metals, etc., so that they cannot move among themselves, it is said to be a solid. All solids, except clay, are expanded by heat, but not equally. (See EXPANSION.) Clay contracts in baking and ever afterwards remains so. Solids are melted by heat, and the process is termed liquefaction. A solid is firm and compact, and, unlike fluids, offers a sensible resistance to penetration and impression. See FLUIDS.