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.

Nitric Acid

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Nitric Acid, a colorless and corrosive liquid. Medieval alchemists called it aqua fortis (strong water). Commercially, nitric acid is made by the action of sulfuric acid on sodium nitrate. Nitric acid is also made by the catalytic oxidation of ammonia. Nitric acid is a strong acid and a strong oxidizing agent. When dropped on the skin, the acid produces a yellow coloration because of the reaction of the acid with certain proteins to form yellow xanthoproteic acid. Nitric acid melts at -42° C (-44° F) and boils at 83° C (181° F).

The salts of nitric acid are called nitrates. Potassium nitrate, or saltpeter, and sodium nitrate are the nitrates of greatest commercial importance. Nearly all nitrates are soluble in water; one of the exceptions is bismuth subnitrate, which is used in medicine for treating intestinal disorders. Amitol, a powerful explosive, is a mixture of ammonium nitrate and trinitrotoluene (TNT). The reaction of nitric acid with organic compounds yields many important nitrates, such as nitroglycerin and nitrocellulose. Calcium, sodium, potassium, and ammonium nitrates are used in fertilizers to provide a source of nitrogen for plant growth.