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.


Formaldehyde, compound of carbon, hydrogen, and oxygen. Formaldehyde was discovered in 1867 by the German chemist August Wilhelm von Hofmann. It is the simplest of the aldehydes. At ordinary temperature it is a gas with a very pungent odor. It can be compressed into a liquid that boils at -21° C (-5.8° F). Formaldehyde is prepared industrially by heating dry air and methyl alcohol vapor in the presence of a catalyst, such as copper or silver. More direct processes, whereby formaldehyde is synthesized from carbon monoxide and hydrogen, have been developed. In one process, water gas is passed over a catalyst at a temperature between 200° and 300° C (392° and 572° F) under a pressure of 7757 torr (150 lb/sq in). Pure formaldehyde is very reactive and polymerizes easily. See Plastics; Polymer.

Formalin is a trade name for a solution containing 40 percent formaldehyde and 60 percent water or water and methyl alcohol; it is employed as a disinfectant, insecticide, fungicide, and deodorant. Formaldehyde is used extensively in the chemical industry in the synthesis of organic compounds. Its most important use is in the manufacture of synthetic resins. Recent tests have indicated that it is a carcinogen.