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.


Acetylene, colorless, odorless, flammable gas. As ordinarily prepared it has an unpleasant odor due to impurities. Acetylene, also known as ethyne, can be prepared from any of various organic compounds by heating them in the absence of air, but it is produced commercially by the reaction of calcium carbide with water or as a by-product of the production of ethylene. Although acetylene can be liquefied at ordinary temperatures with high pressure, it is violently explosive as a liquid. Acetylene gas is usually stored in metal tanks, under pressure, dissolved in liquid acetone. When acetylene is bubbled through a solution of ammonia and cuprous chloride, copper acetylide, a reddish precipitate, is formed. This is used as a test for acetylene. Copper acetylide is explosive when dry.

Acetylene burns in air with a hot and brilliant flame. It was formerly much used as an illuminant and is now mainly used in the oxyacetylene torch, in which acetylene is burned in oxygen, producing a very hot flame used for welding and cutting metal. Acetylene is also used in chemical synthesis, particularly in the manufacture of vinyl chloride for plastics, acetaldehyde, and the neoprene type of synthetic rubber. Acetylene has a melting point of -81° C (-113.8° F) and a boiling point of -57° C (-70.6° F).