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.

Phosphoric Acid

Phosphoric Acid, common acid of phosphorus that is the source of industrially important compounds called phosphates. At room temperature, phosphoric acid is a crystalline material with a specific gravity of 1.83. The solid melts at 42.35° C (108.23° F). Phosphoric acid is usually stored and sold as a solution. Phosphoric acid is made by treating calcium phosphate rock with sulfuric acid, followed by filtration of the resultant liquid to remove calcium sulfate. It can be prepared also by burning phosphorus vapor and treating the resulting oxide with steam. The acid is useful in the laboratory because of its resistance to oxidation, to reduction, and to evaporation. Among the many uses of phosphoric acid are as an ingredient in soft drinks and dental cements, as a catalyst, in rustproofing metals, and in making phosphates, which are used in water softeners, fertilizers, and detergents.


Phosphates are products formed by the replacement of some or all of the hydrogen of a phosphoric acid by metals. Depending on the number of hydrogen atoms that are replaced, the resulting compound is described as a primary, secondary, or tertiary phosphate. Also known as trisodium phosphate, tertiary sodium phosphate is valuable as a detergent and water softener.. Primary and secondary phosphates contain hydrogen and are acid salts. Secondary and tertiary phosphates, with the exception of those of sodium, potassium and ammonium, are insoluble in water; the primary phosphates are more soluble.

Phosphates are important to metabolism in both plants and animals. Bones contain calcium phosphate, and the first step in the oxidation of glucose in the body is formation of a phosphate ester . To provide cattle with phosphate, dicalcium phosphate is used as a food supplement. Primary calcium phosphate is an ingredient of plant fertilizers.

Increasing attention has been focused on the environmentally harmful effects of phosphates in household detergents. Wastewater from laundering agents containing phosphates is known to be a water pollutant because phosphates are a primary nutrient of algae; when it grows in excess, algae can choke a lake or river and draw off needed oxygen from aquatic life.

See Ecology; Environment; Water Pollution.