Matter & Energy

Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.


Sulfur, symbol S, tasteless, odorless, light yellow nonmetallic element. Sulfur is in group 16 (or VIa) of the periodic table. Its atomic number is 16, and its atomic weight is 32.064.

Also called brimstone, sulfur has been known since prehistoric times and is mentioned in the Bible and classical records. Because of its flammability, alchemists regarded sulfur as essential in combustion (see Alchemy).

All forms of sulfur are insoluble in water, but the crystalline forms are soluble in carbon disulfide. When ordinary sulfur melts, it forms a straw-colored liquid that turns darker with additional heating and then finally boils. When molten sulfur is slowly cooled, its physical properties change in accordance with the temperature, pressure, and method of crust formation.

Sulfur ranks 16th in abundance among the elements in the earth's crust and is found widely distributed in both the free and combined states. In combination it occurs in many important metallic sulfides, such as lead sulfide, or galena, zinc blende, copper pyrite, cinnabar, stibnite, and iron pyrite. It is also combined with other elements in the form of sulfates such as barite, celestite and gypsum, and it is present in the molecules of many organic substances such as mustard, eggs, hair, proteins, and oil of garlic.

The most important use of sulfur is in the manufacture of sulfur compounds, such as sulfuric acid, sulfites, sulfates, and sulfur dioxide, all mentioned above. Medicinally, it has assumed importance because of its widespread use in sulfa drugs and in many skin ointments. Sulfur is also employed in the production of matches, vulcanized rubber, dyes, and gunpowder. In a finely divided state and, frequently, mixed with lime, sulfur is used as a fungicide on plants. The salt, sodium thiosulfate commonly called hypo, is used in photography for “fixing” negatives and prints. When combined with various inert mineral fillers, sulfur forms a special cement used to anchor metal objects, such as railings and chains, in stone. Sulfuric acid is one of the most important of all industrial chemicals because it is employed not only in the manufacture of sulfur-containing molecules but also in the manufacture of numerous other materials that do not themselves contain sulfur, such as phosphoric acid.