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.

Acetic Acid

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Acetic Acid, common name of ethanoic acid, a colorless liquid with a sharp, irritating odor and sour taste. In aqueous solution, it functions as a weak acid. Pure acetic acid, because it freezes at slightly below ordinary room temperature, is called glacial acetic acid; mixtures of acetic acid with water solidify at much lower temperatures. Acetic acid is miscible (mixable) in all proportions with water and with many organic solvents.

Acetic acid can be prepared by the action of air on solutions of alcohol in the presence of certain strains of bacteria, such as Bacterium aceti. Dilute solutions (4 to 8 percent) prepared in this way from wine, cider, or malt are called vinegar. Concentrated acetic acid is prepared industrially by several synthetic processes, such as the reaction of methyl alcohol and carbon monoxide (CO) in the presence of a catalyst, or the oxidation of acetaldehyde.

Acetic acid is used in the production of acetate rayon, plastics, photographic film, paint solvents, and pharmaceuticals such as aspirin. Acetic acid boils at 118° C (245° F) and melts at 17° C (62° F).